Multi-layered pipe structure with improved resistance to extraction in biobenzene and its application

Description

[0001] The invention relates to a multilayer structure, in particular in the form of a tube, and its use for transporting fluids, in particular gasoline-type fuel, in particular alcoholic fuel, in particular for motor vehicles.

[0002] The invention relates more particularly to the tubes present within an engine. These tubes may, for example, be intended for the transport of fuels, in particular between the tank and the engine, to the cooling circuit, to the hydraulic system, or even intended for the air conditioning circuit or the transport of a mixture of urea and water.

[0003] For the transport of gasoline and in particular biogasoline, many criteria must be met, in particular good barrier properties (for environmental protection reasons), cold shock, pressure resistance, etc.

[0004] For safety and environmental reasons, particularly with the arrival of new biofuels, car manufacturers require the aforementioned tubes to have specific mechanical characteristics, as well as characteristics of very low permeability and good resistance to the various fuel constituents, these varying according to the country (hydrocarbons, additives, alcohols such as methanol and ethanol, alcohols being able to be the majority components in certain cases), engine lubricating oils and other chemical products likely to be encountered in this environment (battery acid, brake fluids, coolants, metallic salts such as calcium or zinc chloride).

[0005] The characteristics of the specifications commonly required by automobile manufacturers for a tube to be deemed satisfactory are cumulatively the following: good and long-lasting adhesion between the layers, if the tube is a multi-layer tube, especially after being exposed to fuel; good integrity of the connections (tubes with fittings) after circulation of the fuel, i.e. not leading to any leaks; good dimensional stability of the tube, when used with gasoline; good resistance to cold impacts (from -30°C to -40°C approximately), so that the tube does not break; good resistance to heat (approximately 150°C), so that the tube does not deform; good resistance to aging in a hot oxidative environment (for example: hot air from the engine compartment, from 100 to 150°C approximately); good resistance to fuels and their degradation products, particularly with high peroxide contents; very low permeability to fuels, and more particularly good barrier properties to biofuels, both for its polar components (such as ethanol) and for its non-polar components (hydrocarbons);good flexibility of the tube to facilitate assembly, particularly of the fuel supply pipe; good resistance to ZnCl2 (for example, in winter, when the roads are salted, the outside of the tube being exposed to this environment).

[0006] In addition, the desired tubes must avoid the following disadvantages: if the tube is a multi-layer tube, delamination of the layers, particularly internal ones, especially when inserting the fitting (which can lead to leaks); excessive swelling of the tube after aging in gasoline / diesel systems (including for biodiesels or biogasolines), which can lead to leaks or positioning problems under the vehicle.

[0007] Recently, a new problem has emerged, namely the excess extractable material from the multilayer tube after prolonged contact with alcoholic gasoline. These extractable materials are likely to block or clog the injectors of vehicle engines. Car manufacturers, particularly Volkswagen, have therefore implemented new selection criteria for tubes likely to transport gasoline, particularly alcoholic gasoline, in motor vehicles, which are more stringent than before. Thus, the new test developed by the various manufacturers, particularly Volkswagen, consists of determining the proportion of extractables in a gasoline transport tube after placing the inside of the latter in contact with hot alcoholic gasoline for several hours and weighing the evaporation residue of the gasoline contained inside the tube corresponding to the extractables.The tested tube can then only be used for transporting gasoline if the proportion of extractables is as low as possible, in particular less than or equal to 6g / m2 (internal surface area of ​​the tube).

[0008] Currently, there are two types of tubes: single-layer and multi-layer, i.e., tubes made of one or more layers of polymer. For gasoline transportation in particular, the use of multi-layer tubes including a barrier layer is becoming more widespread for ecological reasons.

[0009] Conventionally, the tubes used are manufactured by mono-extrusion, if it is a single-layer tube, or by co-extrusion of the different layers, if it is a multi-layer tube, according to the usual techniques for transforming thermoplastics.

[0010] The structures (MLT) for the transport of gasoline are typically made up of a barrier layer such as EVOH, surrounded on either side by a PA layer (at least one layer) and possibly including layers of binders in the event that the adhesion between the other layers proves insufficient.

[0011] Thus, patent EP 2098580 describes in particular tubes having an EVOH barrier and at least two layers of polyamides, plasticized or not, one being located above the barrier layer and the other being located below the barrier layer.

[0012] However, this type of structure, as well as other MLTs known to those skilled in the art, is no longer suitable for the new extractables test previously cited.

[0013] The present invention intends to solve this new problem by a particular arrangement and constitution of the layers of the multilayer structure.

[0014] The present invention is defined by claims 1-12, and relates to a multilayer tubular structure (MLT) intended for the transport of fluids, in particular gasoline, in particular alcoholic gasoline, comprising from the outside to the inside at least one barrier layer (1) and at least one inner layer (2) located below the barrier layer, said inner layer (2) or all of the layers (2) and any other layers located below the barrier layer, containing on average from 0 to 1.5% by weight of plasticizer relative respectively to the total weight of the composition of the layer (2) or to the total weight of all of the compositions of the layers (2) and any other layers located below the barrier layer, said inner layer (2) mainly comprising at least one polyamide of aliphatic type or consisting of more than 75% of aliphatic units, said aliphatic polyamide being chosen from: a polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA of between 4 and 7; a polyamide denoted B and an average number of carbon atoms per nitrogen atom denoted CB of between 7.5 and 9.5; a polyamide denoted C having an average number of carbon atoms per nitrogen atom denoted Ce of between 10 and 18; provided that when said inner layer (2) comprises at least three polyamides, at least one of said polyamides A, B or C is excluded.

[0015] It would not be outside the scope of the invention if the object intended for the transport of fluids were also used for the storage of fluids.

[0016] The term "fluid" designates a gas used in the automobile or a liquid, in particular a liquid and in particular an oil, a brake fluid, a urea solution, a glycol-based coolant, fuels, in particular light fuels likely to pollute, advantageously fuels except diesel, in particular gasoline or LPG, in particular gasoline and more particularly alcoholic gasoline.

[0017] Air, nitrogen and oxygen are excluded from the definition of said gas.

[0018] Advantageously, said fluid designates fuels, in particular gasoline, in particular alcoholic gasoline.

[0019] The term "gasoline" refers to a mixture of hydrocarbons derived from the distillation of petroleum to which additives or alcohols such as methanol and ethanol may be added, with alcohols being the major components in some cases.

[0020] The term "alcohol-based gasoline" refers to gasoline to which methanol or ethanol has been added. It also refers to E95 gasoline that does not contain petroleum distillation products.

[0021] The expression "all layers (2) and any other layers located below the barrier layer" means all layers present located below the barrier layer.

[0022] The term "barrier layer" refers to a layer having characteristics of low permeability and good resistance to the various constituents of fluids, in particular fuels, i.e. the barrier layer slows down the passage of the fluid, in particular fuel, both for its polar components (such as ethanol) and for its apolar components (hydrocarbons) in the other layers of the structure or even outside the structure. The barrier layer is therefore a layer which above all prevents too much gasoline from being lost into the atmosphere by diffusion, thus preventing atmospheric pollution.

[0023] The barrier materials are impact-modified EVOHs which allow for the creation of less fragile structures.

[0024] The inventors have therefore found that the absence or at least a very low proportion of plasticizer in the inner layer(s), i.e. located under the barrier layer, makes it possible to significantly reduce the proportion of extractables as determined by a test as defined above and in particular by a test which consists of filling a tubular structure with FAM-B type alcoholic essence 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 and finally weighing this residue, the proportion of which must be less than or equal to approximately 6g / m2 of inner tube surface.

[0025] FAM B alcoholic gasoline is described in DIN 51604-1:1982, DIN 51604-2:1984 and DIN 51604-3:1984.

[0026] 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 is prepared by mixing 84.5% FAM A with 15% methanol and 0.5% water.

[0027] In total, FAB consists of 42.3% toluene, 25.4% isooctane, 12.7% di-isobutylene, 4.2% ethanol, 15% methanol and 0.5% water.

[0028] When only one layer (2) is present, the latter is in contact with the fluid.

[0029] In the case where several layers (2) are present, it is possible that one of the inner layers has a proportion of plasticizer greater than 1.5% by weight but in this case, the proportion of plasticizer beyond 1.5% is compensated by the thickness of the layer which is then much thinner so that the average value of plasticizer present in all the inner layers does not exceed 1.5%. The proportion of plasticizer in this layer can then be up to 15% but its thickness does not exceed 10% of the total thickness of the tube, preferably it does not exceed 100µm.

[0030] This much thinner layer can either be in direct contact with the barrier layer, or the innermost layer which is then in contact with the fluid.

[0031] The expression "said inner layer (2) comprising predominantly at least one aliphatic type polyamide" means that said aliphatic type polyamide is present in a proportion of more than 50% by weight in the layer (2). The aliphatic type polyamide is linear and is not of the cycloaliphatic type.

[0032] Advantageously, said polyamide of the majority aliphatic type of the layer(s) (2) also comprises predominantly aliphatic units, namely more than 50% aliphatic units.

[0033] Advantageously, said polyamide of the majority aliphatic type of the layer(s) (2) is made up of more than 75% aliphatic units, preferably said polyamide of the majority aliphatic type of the layer(s) (2) is totally aliphatic.

[0034] According to the present application, the term "polyamide", also noted PA, refers to: homopolymers, copolymers, or copolyamides, based on different amide units, such as for example copolyamide 6 / 12 with amide units derived from lactam-6 and lactam-12, polyamide alloys, provided that polyamide is the majority constituent.

[0035] 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-6.12 where the polyamide units are the same as those of PA6.12.

[0036] Homopolyamides, copolyamides and alloys are also distinguished by their number of carbon atoms per nitrogen atom, knowing that there are as many nitrogen atoms as amide groups (-CO-NH-).

[0037] A high-carbon polyamide is a polyamide with a high ratio of carbon atoms (C) to nitrogen atoms (N). These are polyamides with approximately at least 9 carbon atoms per nitrogen atom, such as polyamide-9, polyamide-12, polyamide-11, polyamide-10.10 (PA10.10), copolyamide 12 / 10.T, copolyamide 11 / 10.T, polyamide-12.T, polyamide-6.12 (PA6.12). T represents terephthalic acid.

[0038] 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.

[0039] A low-carbon polyamide is a polyamide with a low ratio of carbon atoms (C) to nitrogen atoms (N). These are polyamides with approximately less than 9 carbon atoms per nitrogen atom, such as polyamide-6, polyamide-6.6, polyamide-4.6, copolyamide-6.T / 6.6, copolyamide 6.I / 6.6, copolyamide 6.T / 6.I / 6.6, polyamide 9.T. I stands for isophthalic acid.

[0040] In the case of a homopolyamide of type PA-XY, with X designating a unit obtained from a diamine and Y designating a unit obtained from a diacid, the number of carbon atoms per nitrogen atom is the average of the numbers of carbon atoms present in the unit resulting from diamine X and in the unit resulting from diacid Y. Thus PA6.12 is a PA with 9 carbon atoms per nitrogen atom, in other words a C9 PA. PA6.13 is C9.5.

[0041] In the case of copolyamides, the number of carbon atoms per nitrogen atom is calculated according to the same principle. The calculation is carried out in molar proportion to the different amide units. In the case of a copolyamide with non-amide units, the calculation is carried out only on the share of amide units. Thus, for example, PEBA-12, which is a block copolymer of amide 12 units and ether units, the average number of carbon atoms per nitrogen atom will be 12, as for PA12; for PEBA-6.12, it will be 9, as for PA6.12.

[0042] Thus, highly carbon-based polyamides such as polyamide PA12 or 11 adhere with difficulty to an EVOH polymer, to a low-carbon polyamide such as polyamide PA6, or even to an alloy of polyamide PA6 and polyolefin (such as, for example, Orgalloy ® marketed by the Arkema company).

[0043] However, it is observed that the tube structures currently proposed are not satisfactory for use dedicated to biofuels, the requirements of the specifications of the automobile manufacturers recalled above cannot all be met simultaneously.

[0044] Biofuels are not only derived from petroleum, but also contain a proportion of polar products such as plant-based alcohols, such as ethanol or methanol, of at least 3%. This percentage can rise to 85% or even 95%.

[0045] In addition, the fuel circulation temperature tends to rise due to new engines (more confined, operating at higher temperatures).

[0046] In an advantageous embodiment, said inner layer (2) or each of the layers (2) and of the other possible layers located below the barrier layer, contains from 0 to 1.5% by weight of plasticizer relative respectively to the total weight of the composition of the layer (2) or to the total weight of each of the compositions of the layers (2) and of the other possible layers located below the barrier layer.

[0047] In an advantageous embodiment, in the multi-layer tubular structure (MLT) as defined above, said inner layer (2) or each of the layers (2) and of the other possible layers located below the barrier layer is (are) free of plasticizer.

[0048] In this embodiment, all the layers located under the barrier layer are completely free of plasticizer and constitute one of the preferred structures of the invention. The present invention relates to a multilayer tubular structure (MLT) as defined above, in which at least one outermost layer (3) located above the barrier layer is present, said outer layer (3) comprising predominantly at least one polyamide of aliphatic type or consisting of more than 75% of aliphatic units, in particular said aliphatic polyamide having an average number of carbon atoms per nitrogen atom of 9.5 to 18, advantageously 11 to 18.

[0049] The expression "said outer layer (3) comprising predominantly at least one aliphatic type polyamide" means that said aliphatic type polyamide is present in a proportion of more than 50% by weight in the layer (3). The aliphatic type polyamide is linear and is not of the cycloaliphatic type.

[0050] Advantageously, said polyamide of the majority aliphatic type of the layer(s) (3) also comprises predominantly aliphatic units, namely more than 50% aliphatic units.

[0051] Advantageously, said polyamide of the majority aliphatic type of the layer(s) (3) is made up of more than 75% aliphatic units, preferably said polyamide of the majority aliphatic type of the layer(s) (3) is totally aliphatic.

[0052] Advantageously, said polyamide of the majority aliphatic type of the layer(s) (2) and of the layer(s) (3) also comprises predominantly aliphatic units, namely more than 50% aliphatic units.

[0053] Advantageously, said polyamide of the majority aliphatic type of the layer(s) (2) and of the layer(s) (3) is made up of more than 75% aliphatic units, preferably said polyamide of the majority aliphatic type of the layer(s) (2) and of the layer(s) (3) is totally aliphatic.

[0054] Advantageously, the present invention relates to a multi-layer tubular structure (MLT) as defined above, in which said outer layer (3) comprises from 0 to 15% of plasticizer relative to the total weight of the composition of the layer (3), or in which all of the outer layers comprise on average from 0 to 5% of plasticizer.

[0055] It is possible to have a higher proportion of plasticizer in the outer layer(s), i.e. the layer(s) located above the barrier layer without significantly increasing the proportion of extractables.

[0056] As already indicated above for the layers (2), in the case where several layers (3) are present, it is possible that one of the outer layers has a significant proportion of plasticizer such as 15% by weight but in this case, the proportion of plasticizer is compensated by the thickness of the layer which is then much thinner so that the average value of plasticizer present in all the inner layers does not exceed 5%. The proportion of plasticizer in this layer can then be up to 15% but its thickness does not exceed 20% of the total thickness of the tube, preferably it does not exceed 200µm.

[0057] The present invention relates to a multi-layer tubular structure (MLT) comprising a layer (3) as defined above, in which at least a second outer layer (3`) located above the barrier layer is present, and located above the layer (3), said layer (3') being plasticized, said plasticizer being in particular present in a proportion of 1.5% to 15% by weight relative to the total weight of the composition of said layer, the thickness of said layer (3') preferably represents up to 20% of the total thickness of the tubular structure, in particular up to 200µm.

[0058] The layer (3') comprises, like the layer (3), mainly an aliphatic type polyamide, that is to say that said aliphatic type polyamide is present in a proportion of more than 50% by weight in the layer (3'). The aliphatic type polyamide is linear and is not of the cycloaliphatic type.

[0059] Advantageously, said polyamide of the majority aliphatic type of the layer(s) (3') also comprises predominantly aliphatic units, namely more than 50% aliphatic units.

[0060] Advantageously, said polyamide of the majority aliphatic type of the layer(s) (3') is made up of more than 75% aliphatic units, preferably said polyamide of the majority aliphatic type of the layer(s) (3') is totally aliphatic.

[0061] In another embodiment, the present invention relates to a multi-layer tubular (MLT) structure, in which the layer(s) (3) comprises up to 1.5% by weight of plasticizer, relative to the total weight of the composition of said layer or of all the compositions of the layers (3).

[0062] Advantageously, the multi-layer tubular structure (MLT) comprises a single layer (3) and is free of plasticizer.

[0063] Advantageously, the multi-layer tubular structure (MLT) comprises a single layer (3) and a single layer (2), the layers (2) and (3) being free of plasticizer.

[0064] In another embodiment, the present invention relates to a multi-layer tubular (MLT) structure, in which the plasticizer level of all the layers located above the barrier layer is at most 5% by weight relative to the total weight of the compositions of all the layers located above the barrier layer.

[0065] In another embodiment, the present invention relates to a multi-layer tubular structure (MLT), in which the layer (3') is the outermost and is the only plasticized one, the layer(s) (3) being devoid of plasticizer.

[0066] The proportion of plasticizer can represent up to 15% by weight of the total weight of the composition of the layer (3'). The higher the proportion of plasticizer, the thinner the layer (3') will be, with a thickness of said layer (3') preferably representing up to 20% of the total thickness of the tubular structure, in particular up to 200µm.

[0067] Advantageously, the multi-layer tubular structure (MLT) consists of four layers, from the outside to the inside (3') / / (3) / / (1) / / (2), layer (3') being the only one plasticized in proportions as defined above, layer (3) and layer (2) being free of plasticizer.

[0068] A multi-layer tubular structure (MLT) consisting of four layers from the outside to the inside (3') / / (3) / / (1) / / (2) has the advantage of having an elongation at break at t = 0 when the structure is very dry with a very low humidity level between 0 and 30% relative humidity, which is very good and notably better than a structure whose layers (3'), (3) and (2) are devoid of plasticizer.

[0069] Advantageously, in this latter embodiment, the layer (3') is the outermost and the polyamide of the latter is a long-chain polyamide, i.e. an average number of carbon atoms per nitrogen atom noted Ce of from 9.5 to 18, the layer (3) is located between the barrier layer and the layer (3') and the polyamide of this layer (3) is a short-chain polyamide, i.e. an average number of carbon atoms per nitrogen atom noted Ca of from 4 to 9.

[0070] Advantageously, in this latter embodiment, the layer (3') has a thickness of 100 to 200 µm, the layer (3) has a thickness of at least 200 µm, the layer (1) has a thickness of 100 to 200 µm.

[0071] Advantageously, in this latter embodiment, the layer (3') is the outermost and the polyamide of the latter is a long-chain polyamide, i.e. an average number of carbon atoms per nitrogen atom noted Ce of between 9.5 and 18, the layer (3) is located between the barrier layer and the layer (3') and the polyamide of this layer (3) is a short-chain polyamide, i.e. an average number of carbon atoms per nitrogen atom noted of between 4 and 9, the layer (3') has a thickness of between 100 and 200µm, the layer (3) has a thickness of at least 200µm, the layer (1) has a thickness of between 100 and 200µm.

[0072] Advantageously, the multi-layer tubular structure (MLT) is made up of five layers from the outside to the inside (3') / / (3) / / (1) / / (2) / / (2'), layer (3') being the only one plasticized in proportions as defined above, layer (3) and layers (2) and (2') being free of plasticizer, layer (2') being a polyamide as defined for layer (2) but different from that of layer (2). This type of structure makes it possible to increase the elongation at break in very low humidity conditions) without over-stiffening the structure.

[0073] Regardless of the number of layers, three, four, five or more, the preferred tubular structures are those containing the least possible plasticizer, and preferably the least plasticizer in the innermost layers, i.e. those closest to the fluid. These structures may be the following: Multi-layer tubular structure (MLT) containing no more than 1.5% of plasticizer, in the first 50% of its thickness from the inner face in contact with the fluid. Multi-layer tubular structure (MLT) containing no more than 1.5% of plasticizer, in the first 75% of its thickness from the inner face in contact with the fluid. Multi-layer tubular structure (MLT) containing no more than 1.5% of plasticizer, in the first 85% of its thickness from the inner face in contact with the fluid. Multi-layer tubular structure (MLT) free of plasticizer, in the first 50% of its thickness from the inner face in contact with the fluid. Multi-layer tubular structure (MLT) free of plasticizer, in the first 75% of its thickness from the inner face in contact with the fluid.Multi-layer tubular structure (MLT) free of plasticizer, in the first 85% of its thickness from the internal face in contact with the fluid.

[0074] The present invention relates to a multi-layer tubular structure (MLT) as defined above, in which at least one layer (4) is present, said layer (4) containing no more than 15% by weight of plasticizer, preferably no more than 1.5% by weight of plasticizer, relative to the total weight of the constituents of the layer (4), advantageously the layer (4) is free of plasticizer, said layer (4) comprising predominantly at least one polyamide of aliphatic type or consisting of more than 75% of aliphatic units, said aliphatic polyamide being chosen from: a polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA of from 4 to 7; a polyamide denoted B and an average number of carbon atoms per nitrogen atom denoted CB of from 7.5 to 9.5; a polyamide denoted C having an average number of carbon atoms per nitrogen atom denoted CC of from 10 to 18; provided that when said layer (4) comprises at least three polyamides, at least one of said polyamides A, B or C is excluded, said layer (4) being located between the barrier layer (1) and the inner layer (2) and / or between the outer layer (3) and the barrier layer (1); or said layer (4) is a binder layer whose thickness represents up to 15% of the structure (MLT).

[0075] Layer (4) when it is not a binder layer is an aliphatic type polyamide as defined for layers (2), (3) and (3').

[0076] Advantageously, the tubular structure of the invention is a four-layer structure consisting from the outside to the inside of the following layers: (3) / / (4) / / (1) / / (2), layer (3) being plasticized up to 15% as above and thin and layer (4) when it is different from the binder layer as defined above is devoid of plasticizer as well as layer (2).

[0077] Advantageously, the tubular structure of the invention is a four-layer structure consisting from the outside to the inside of the following layers: (3) / / (1) / / (4) / / (2), layer (3) being plasticized up to 15% by weight as above and preferably thin and layer (4) when it is different from the binder layer, as defined above, is free of plasticizer as well as layer (2).

[0078] However, this layer (3) plasticized up to 15% by weight must not be too thin otherwise the barrier layer is too little in the center and the MLT structure risks not being good enough in shock. On the other hand it can be very thin if there is an additional thick layer (not plasticized) between layer (3) and layer (1), so that layer (1) is not too off-center.

[0079] Another layer (2') and / or a layer (3') may also be present in these two types of four-layer structures.

[0080] Said layer (4) may also be a binder as described, in particular in patents EP 1452307 and EP1162061, EP 1216826 and EP0428833.

[0081] It is implied that layers (3) and (1) or (1) and (2) adhere to each other. The binder layer is intended to be inserted between two layers that do not adhere or adhere only with difficulty to each other.

[0082] The binder may be, for example, but not limited to, a composition based on 50% copolyamide 6 / 12 (70 / 30 ratio by mass) of Mn 16000, and 50% copolyamide 6 / 12 (30 / 70 ratio by mass) of Mn 16000, a composition based on PP (polypropylene) grafted with maleic anhydride, known as Admer QF551A from the company Mitsui, a composition based on PA610 (of Mn 30000, and as defined elsewhere) and 36% PA6 (of Mn 28000) and 1.2% organic stabilizers (consisting of 0.8% Lowinox 44B25 phenol from the company Great Lakes, 0.2% phosphite Irgafos 168 from Ciba, 0.2% of anti-UV Tinuvin 312 from Ciba), a composition based on PA612 (of Mn 29000, and as defined elsewhere) and 36% of PA6 (of Mn 28000, and as defined elsewhere) and 1.2% of organic stabilizers (consisting of 0.8% of phenol Lowinox 44B25 from Great Lakes, 0.2% of phosphite Irgafos 168 from Ciba, 0.2% of anti-UV Tinuvin 312 from the company Ciba), a composition based on PA610 (of Mn 30000, and as defined elsewhere) and 36% of PA12 (of Mn 35000, and as defined elsewhere) and 1.2% of organic stabilizers (consisting of 0.8% of phenol Lowinox 44B25 from the company Great Lakes, 0.2% of phosphite Irgafos 168 from the company Ciba, 0.2% of anti-UV Tinuvin 312 from the company Ciba), a composition based on 40% PA6 (of Mn 28000, and as defined elsewhere), 40% of PA12 (of Mn 35000, and as defined elsewhere) and 20% of functionalized EPR Exxelor VA1801 (Exxon company) and 1.2% organic stabilizers (consisting of 0.8% Lowinox 44B25 phenol from Great Lakes company, 0.2% Irgafos 168 phosphite from Ciba company, 0.2% Tinuvin 312 UV inhibitor from Ciba company) or a composition based on 40% PA6.10 (of Mn 30000, and as defined elsewhere), 40% of PA6 (of Mn 28000, and as defined elsewhere) and 20% of ethylene / ethyl acrylate / anhydride type impact modifier in a mass ratio of 68.5 / 30 / 1.5 (MFI 6 at 190°C under 2.16 kg), and 1.2% of organic stabilizers (consisting of 0.8% of Lowinox 44B25 phenol from Great Lakes, 0.2% of Irgafos 168 phosphite from Ciba, 0.2% of Tinuvin 312 UV stabilizer from Ciba).

[0083] In another embodiment, the present invention relates to a multilayer tubular structure (MLT) as defined above, in which a layer (4') is present, said layer (4') comprising predominantly at least one polyamide of aliphatic type or consisting of more than 75% of aliphatic units, said aliphatic polyamide being chosen from: a polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA of from 4 to 7; a polyamide denoted B and an average number of carbon atoms per nitrogen atom denoted CB of from 7.5 to 9.5; a polyamide denoted C having an average number of carbon atoms per nitrogen atom denoted CC of from 10 to 18; provided that when said layer (4') comprises at least three polyamides, at least one of said polyamides A, B or C is excluded, or said layer (4') is a binder layer whose thickness represents up to 15% of the structure (MLT), said at least one polyamide of said layer (4') being able to be identical to or different from said polyamide of layer (4); said layer (4') being located between the outer layer (3) and the barrier layer (1) and said binder layer (4) being located between the barrier layer (1) and the inner layer (2). Layer (4') may or may not contain a plasticizer. Advantageously, it is free of plasticizer, just like layer (2) and layer (4), layer (3) being plasticized but thin as defined above. In another embodiment, the present invention relates to a multi-layer tubular (MLT) structure as defined above, wherein the polyamide of the inner layer (2) or the polyamide of the outer layer (3) is a fully aliphatic polyamide, preferably the polyamide of the inner layer (2) and the polyamide of the outer layer (3) are fully aliphatic polyamides.

[0084] In another embodiment, the present invention relates to a multi-layer tubular structure (MLT) as defined above, in which a second barrier layer (5) is present, said second barrier layer (5) being adjacent or not to the first barrier layer (1) and located below said barrier layer (1). It may be of interest in particular for alcoholic gasolines, and especially for those containing methanol) to put a second barrier layer to further limit the diffusion of the gasoline into the atmosphere and / or to reduce the extractable rate.

[0085] This second barrier layer is different from the first barrier layer (1).

[0086] In another embodiment, the present invention relates to a multi-layer tubular (MLT) structure as defined above, wherein the barrier layer (1) is an EVOH layer.

[0087] In another embodiment, the present invention relates to a multi-layer tubular (MLT) structure as defined above, wherein the EVOH is an EVOH comprising up to 27% ethylene.

[0088] In another embodiment, the present invention relates to a multi-layer tubular (MLT) structure as defined above, wherein the EVOH is an EVOH comprising an impact modifier.

[0089] In another embodiment, the present invention relates to a multi-layer tubular (MLT) structure as defined above, wherein the barrier layer (1) is a polyphthalamide (PPA) layer.

[0090] The term PPA means a composition based mainly on a polyamide comprising a majority of units which comprise at least one aromatic monomer, in particular polyphthalamide of the copolyamide 6.T / x type (where x denotes one or more comonomoers) such as Zytel HTN from the company Dupont, such as Grivory HT from the company Ems, such as Amodel from the company Solvay, such as Genestar from the company Kuraray, such as PPA compositions based on coPA6T / 6I, coPA6T / 66, coPA6T / 6, coPA6T / 6I / 66, PPA9T, coPPA9T / x, PPA10T, coPPA10T / x.

[0091] In another embodiment, the present invention relates to a multi-layer tubular structure (MLT) as defined above, in which the barrier layer (1) is an EVOH layer and the second barrier layer (5) is a PPA or fluoropolymer layer, in particular of the ETFE, EFEP, CPT type.

[0092] Advantageously, the barrier layer (1) is an EVOH layer and the second barrier layer (5) is a PPA layer.

[0093] In another embodiment, the present invention relates to a multi-layer tubular (MLT) structure as defined above, wherein the barrier layer (1) is an EVOH layer and the second barrier layer (5) is a PPA layer.

[0094] In another embodiment, the present invention relates to a multi-layer tubular structure (MLT) as defined above, in which the barrier layer (1) is an EVOH layer and the second barrier layer (5) is a fluoropolymer layer, in particular of the ETFE, EFEP, CPT type.

[0095] Advantageously, in the multilayer tubular structure (MLT) as defined above, the polyamide of the inner layer (2) is a composition based on a polyamide chosen from A, B or C as defined above, in particular PA6, PA66, PA6 / 66, PA11, PA610, PA612, PA1012, the corresponding copolyamides and the mixtures of said polyamides or copolyamides, the polyamides obtained from a lactam being advantageously washed.

[0096] Advantageously, in the multilayer tubular structure (MLT) as defined above, the polyamide of the outer layer (3) is a polyamide chosen from Bou C as defined above, in particular PA 11, PA12, PA610, PA612, PA1012, the corresponding copolyamides and the mixtures of said polyamides or copolyamides, the polyamides obtained from a lactam being advantageously washed.

[0097] Advantageously, in the multilayer tubular structure (MLT) as defined above, the polyamide of the inner layer (2) is a composition based on a polyamide chosen from A, B or C as defined above, in particular PA6, PA66, PA6 / 66, PA11, PA610, PA612, PA1012, the corresponding copolyamides and the mixtures of said polyamides or copolyamides, the polyamides obtained from a lactam being advantageously washed, and the polyamide of the outer layer (3) is a polyamide chosen from B or C as defined above, in particular PA 11, PA12, PA610, PA612, PA1012, the corresponding copolyamides and the mixtures of said polyamides or copolyamides, the polyamides obtained from a lactam being advantageously washed.

[0098] In another embodiment, the present invention relates to a multi-layer tubular (MLT) structure as defined below, wherein the polyamide of the inner layer (2) or of at least one of the other layers (2) is a conductive polyamide.

[0099] When the tubular structure of the invention comprises several layers (2), the conductive layer is the one which is the most internal, that is to say in contact with the fluid.

[0100] Advantageously, in the multilayer tubular structure (MLT) as defined above, the polyamide of layer (4) and / or (4') is a mixture of a polyamide having an average number of carbon atoms per nitrogen atom of 10 or more and a polyamide having an average number of carbon atoms per nitrogen atom of 6 or less, for example PA12 and PA6 and an anhydride functionalized (co)polyolefin.

[0101] Advantageously, in the multilayer tubular structure (MLT) as defined above, the polyamide of layer (4) and / or (4') is chosen from the binary mixtures: PA6 and PA12, PA6 and PA612, PA6 and PA610, PA12 and PA612, PA12 and PA610, PA1010 and PA612, PA1010 and PA610, PA1012 and PA612, PA1012 and PA610.

[0102] In another embodiment, the present invention relates to a multi-layer tubular (MLT) structure as defined above, wherein at least one of the layers (2), (3), (3'), (4) and (4') comprises at least one impact modifier and / or at least one additive.

[0103] It is quite obvious that the impact modifier or additive is not a plasticizer.

[0104] Advantageously, layers (2) and (3) comprise at least one impact modifier and / or at least one additive.

[0105] Advantageously, layers (2), (3) and (3') comprise at least one impact modifier and / or at least one additive.

[0106] Advantageously, layers (2), (3), (3') and (4) comprise at least one impact modifier and / or at least one additive.

[0107] Advantageously, layers (2), (3), (3'), (4) and (4') comprise at least one impact modifier and / or at least one additive.

[0108] In another embodiment, the present invention relates to a multi-layer tubular (MLT) structure as defined above, wherein the structure comprises three layers in the following order (3) / / (1) / / (2), wherein layers (3) and / or (2) contain no more than 1.5% by weight of plasticizer, relative to the total weight of the composition of each layer, in particular layer (3) and / or (2) is (are) free of plasticizer.

[0109] In another embodiment, the present invention relates to a multi-layer tubular (MLT) structure as defined above, wherein the structure comprises four layers in the following order (3') / / (3) / / (1) / / (2), layer (3') being as defined above, layer (2) and / or (3) containing no more than 1.5% by weight of plasticizer, relative to the total weight of the composition of each layer, in particular layer (2) and / or (3) is (are) free of plasticizer.

[0110] In another embodiment, the present invention relates to a multi-layer tubular (MLT) structure as defined above, wherein the structure comprises five layers in the following order: (3') / / (3) / / (1) / / (5) / / (2) wherein layer (1) is an EVOH layer, layer (5) is a PPA layer, layer (2) containing no more than 1.5% by weight of plasticizer, relative to the total weight of the composition of each layer, in particular layer (2) is free of plasticizer, layer (3) and (3') comprising plasticizer; or (3') / / (3) / / (1) / / (2) / / (5) wherein layer (1) is an EVOH layer, layer (5) is a PPA layer, layer (2) containing no more than 1.5% by weight of plasticizer, relative to the total weight of the composition of each layer, in particular layer (2) is free of plasticizer, layer (3) and (3') comprising plasticizer;or (3) / / (4') / / (1) / / (4) / / (2) wherein layer (3) is as defined in claim 3, layer (2) and (4) containing no more than 1.5% by weight of plasticizer, relative to the total weight of the composition of each layer, in particular layer (2) and / or (4) is (are) free of plasticizer, layer (4') comprising plasticizer, in particular layer (4') is free of plasticizer. ; According to another embodiment, the present invention relates to a multi-layer tubular (MLT) structure as defined above, wherein the structure comprises the layers in the following order: (3') / / (3) / / (4') / / (1) / / (4) / / (2) wherein layers (3) and (3') are as defined above, layer (2) and (4) containing no more than 1.5% by weight of plasticizer, relative to the total weight of the composition of each layer, in particular layer (2) and / or (4) is (are) free of plasticizer, layer (4') comprising plasticizer, in particular layer (4') is free of plasticizer. In particular, said layer (3') of the above six-layer structure is plasticized, said plasticizer being in particular present in a proportion of 1.5% to 15% by weight relative to the total weight of the composition of said layer, the thickness of said layer (3') preferably represents up to 20% of the total thickness of the tubular structure, in particular up to 200µm, in particular the layer (3') is the outermost and is the only plasticized one, the layer(s) (3) being free of plasticizer.

[0111] According to another aspect, the present invention relates to the use of a multi-layer tubular structure MLT, as defined above, for the transport of fluids, in particular gasoline.

[0112] An extractable value less than or equal to approximately 6g / m2 of internal tube surface area indicates that the proportion of extractables is very low and will thus avoid clogging the injectors. EXAMPLES (ONLY EXAMPLES 11-14 ARE IN ACCORDANCE WITH THE INVENTION)

[0113] The invention will now be described in more detail with the aid of the following examples which are not limiting.

[0114] 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.

[0115] 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.

[0116] 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. For structures with 6 layers, an additional extruder is connected and a spiral mandrel is added to the existing head to produce the inner layer, in contact with the fluid.

[0117] 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.

[0118] 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. Generally, the line speed is typically 20m / min. It generally varies between 5 and 100m / min.

[0119] The screw speed of extruders depends on the layer thickness and screw diameter as is known to those skilled in the art.

[0120] Generally speaking, the temperatures of the extruders and tools (head and connector) must be set so as to be sufficiently higher than the melting temperature of the compositions in question, so that they remain in the molten state, thus preventing them from solidifying and blocking the machine.

[0121] The tubular structures were tested on different parameters (Table I). The amount of extractables was determined, the barrier properties were evaluated as well as the impact and bursting. Table II indicates the tests used and the classification of the results. TABLEAU I Examples and counterexamples Extractable Barrier Shock Burst (1) Counter example 1: PA12-TL / binder / EVOH / binder / PA12-TL 400 / 50 / 150 / 50 / 350µm >50 GOOD GOOD GOOD Counter example 2: PA12-TL / binder / EVOH / binder-Noplast / PA12-TL 400 / 50 / 150 / 50 / 350µm >50 GOOD GOOD GOOD Counter example 3: PA12-NoPlast / binder-NoPlast / EVOH / binder-NoPlast / PA12-TL 400 / 50 / 150 / 50 / 350µm >50 GOOD GOOD GOOD Counter example 4: PA12-NoPlast / binder-NoPlast / EVOH / binder-no-plast / PA11-TL 400 / 50 / 150 / 50 / 350µm >30 GOOD GOOD GOOD Counter example 5: PA12-NoPlast / binder-NoPlast / EVOH / binder-no-plast / PA610-TL 400 / 50 / 150 / 50 / 350µm >30 GOOD GOOD GOOD Ex.1: PA12-NoPlast / binder-NoPlast / EVOH / binder-NoPlast / PA610-NoPlast 400 / 50 / 150 / 50 / 350µm <5.5 GOOD GOOD GOOD Ex.2: PA12-NoPlast / binder-NoPlast / EVOH / binder-NoPlast / PA612-NoPlast 400 / 50 / 150 / 50 / 350µm <6 GOOD GOOD GOOD Ex. 3 PA12-NoPlast / binder-NoPlast / EVOH / binder- NoPlast / coPA612-6T-NoPlast 400 / 50 / 150 / 50 / 350µm <6 GOOD GOOD GOOD Ex. 4 PA12-NoPlast / binder-NoPlast / EVOH / PA6-NoPlast 400 / 50 / 150 / 400µm <6 GOOD GOOD GOOD Ex. 5 PA12-NoPlast / binder-NoPlast / EVOH / PA610-NoPlast 400 / 50 / 150 / 400µm) <5.5 GOOD GOOD GOOD Ex. 6 PA610-NoPlast / EVOH / PA610-NoPlast 450 / 150 / 400 µm <5.5 GOOD limit Alright Ex. 7 PA11-TL / PA610-NoPlast / EVOH / PA610-NoPlast 150 / 300 / 150 / 400µm) <5.5 GOOD GOOD Alright Ex. 8 PA11-TL / PA610-NoPlast / EVOH / PA610-NoPlast / PA11-NoPlast 150 / 300 / 150 / 250 / 150µm <5.5 GOOD Alright Alright Ex. 9 PA12-NoPlast / binder-NoPlast / EVOH / binder-NoPlast / PA610-NoPlast 550 / 50 / 150 / 50 / 200µm <4.5 GOOD limit GOOD Ex. 10 PA12-NoPlast / binder-NoPlast / EVOH24 / binder-NoPlast / PA610-NoPlast 400 / 50 / 150 / 50 / 350µm <5.5 Alright GOOD GOOD Ex. 11 PA12-NoPlast / binder-NoPlast / EVOHhi / binder-NoPlast / PA610-NoPlast (550 / 50 / 150 / 50 / 200µ) <4.5 GOOD GOOD GOOD Ex. 12 PA12-TL / binder / EVOHhi / binder-NoPlast / PA610-NoPlast 550 / 50 / 150 / 50 / 200µ <5.5 GOOD GOOD GOOD Ex. 13 PA12-TL / binder2 / EVOHhi / binder2-NoPlast / PA610-NoPlast 550 / 50 / 150 / 50 / 200µ <5.5 GOOD GOOD GOOD Ex. 14 PA12-TL / binder / EVOHhi / binder-NoPlast / PA612-NoPlast 550 / 50 / 150 / 50 / 200µ <6 GOOD GOOD GOOD Ex. 15 PA12-TL / PPA10T / PA11-NoPlast 600 / 250 / 150µm <5 limit GOOD GOOD Ex. 16 PA12-TL / binder / EVOH / PA610-NoPlast / PPA10T 350 / 50 / 100 / 400 / 100µm <3 Alright GOOD Alright Ex. 17 PA12-TL / binder / EVOH / PPA10T / PA610-NoPlast 350 / 50 / 100 / 100 / 400µm <5.5 Alright GOOD Alright Ex. 18 PA12-TL / binder / EVOH / PA610-NoPlast / EFEPc 350 / 50 / 100 / 400 / 100µ <3 Alright GOOD Alright Ex. 19 PA11-TL / PA610-NoPlast / EVOH / PA610-NoPlast / PA11cond-NoPlast 400 / 50 / 150 / 300 / 100 <5.5 GOOD limit Alright (1) Burst is the burst after at least 96 hours with FAM-B bio-essence inside, so we are looking for a value high enough to hold the pressure. TABLE II Properties Very good (VG) Good (B) Limit (AB) Bad (Mv) Bio-essence barrier CE10 60°C g / m 2< .24h, 150µm thick barrier <0.2 0.2-1 1-3 > 3 Extractables: <4.5 g / m 2< of tube surface (internal surface int) 4.5-5.5 g / m 2< of tube surface (internal surface int) 5.5-6 g / m 2< of tube surface (internal surface int) > 6 g / m 2 < of tube surface (internal surface int) 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 of which is weighed, the latter having to be less than or equal to 6g / m2 (internal surface area of ​​the tube) VW shock - 40°C VW standard TL52435 2010 <4% breakage <11% breakage <21% breakage >22% breakage Burst after aging standard VW TL52435 2010 >30 N / mm 2< (MPa) 30-27 N / mm 2< (MPa) 27-25 N / mm 2< (MPa) <25 N / mm 2< (MPa)

[0122] The measurements of permeability to gasolines (Bio-gasoline barrier) are determined at 60°C using a gravimetric method with CE10: isooctane / toluene / ethanol = 45 / 45 / 10 vol.%.

[0123] 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 steady-state value is considered to be the permeability of the material. Compositions

[0124] PA12-TL: refers to a composition based on polyamide 12 of Mn (number-average molecular weight) 35000, containing 6% BBSA (benzyl butyl sulfonamide) plasticizer, and 6% Exxelor VA1801 anhydride-functionalized EPR (Exxon company), and 1.2% organic stabilizers (consisting of 0.8% Lowinox 44B25 phenol from Great Lakes company, 0.2% Irgafos 168 phosphite from Ciba company, 0.2% Tinuvin 312 UV stabilizer from Ciba company). The melting temperature of this composition is 175°C. PA12-NoPlast = PA12-TL without the plasticizer (the latter is replaced by the same % in PA12) PA11-TL designates a composition based on polyamide 11 of Mn (number-average molecular weight) 29000, containing 5% BBSA plasticizer (benzyl butyl sulfonamide), 6% ethylene / ethyl acrylate / anhydride type impact modifier in a mass ratio of 68.5 / 30 / 1.5 (MFI 6 at 190°C under 2.16 kg), and 1.2% organic stabilizers (consisting of 0.8% Lowinox 44B25 phenol from Great Lakes, 0.2% Irgafos 168 phosphite from Ciba, 0.2% Tinuvin 312 UV inhibitor from Ciba). The melting temperature of this composition is 185°C. PA11-NoPlast = PA11-TL without the plasticizer (the latter is replaced by PA11) PA610-NoPlast = PA610-TL without the plasticizer (the latter is replaced by PA610) · PA12: Polyamide 12 of Mn (number-average molecular weight) 35000.The melting temperature is 178°C, its enthalpy of fusion is 54kJ / m2 · PA11: Polyamide 11 of Mn (molecular weight by number) 29000. The melting temperature is 190°C, its enthalpy of fusion is 56kJ / m2 · PA610: Polyamide 6.10 of Mn (molecular weight by number) 30000. The melting temperature is 223°C, its enthalpy of fusion is 61kJ / m2 · PA612: Polyamide 6.12 of Mn (molecular weight by number) 29000. The melting temperature is 218°C, its enthalpy of fusion is 67kJ / m2 · PA6: Polyamide 6 of Mn (molecular weight by number) 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 type Exxellor VA1801 from the company Exxon.

[0125] Organic stabilizer = 1.2% 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) coPA612-6T-NoPlast = coPA6.12 / 6.T with 20% mol of 6.T (so 80% mol of 6.12) (this coPA makes MFI 235°C, 5kg = (T° melting = 200°C) + 20% EPR1 + stab orga PPA10T = coPA10.T / 6.T of molar ratio 60 / 40 T melting 280°C + 18% EPR1 + stab orga PA11cond-noplast = PA11 of Mn 15000 + 9%EPR1 + 22% carbon black type Ensaco 200

[0126] Binder = Composition based on 43.8% PA612 (tq defined elsewhere), 25% PA6 (tq defined elsewhere) and 20% EPR1 type impact modifier, and 1.2% organic stabilizers (consisting of 0.8% Lowinox 44B25 phenol from Great Lakes, 0.2% Irgafos 168 phosphite from Ciba, 0.2% Tinuvin 312 UV stabilizer from Ciba), and 10% BBSA plasticizer (benzyl butyl sulfonamide).

[0127] Binder-NoPlast = Composition based on 48.8% PA612 (tq defined elsewhere), 30% PA6 (tq defined elsewhere), and 20% EPR1 type impact modifier, and 1.2% organic stabilizers (consisting of 0.8% Lowinox 44B25 phenol from Great Lakes, 0.2% Irgafos 168 phosphite from Ciba, 0.2% Tinuvin 312 UV stabilizer from Ciba).

[0128] Binder 2 = Composition based on 43.8% PA610 (tq defined elsewhere), 25% PA6 (tq defined elsewhere) and 20% impact modifier type EPR1, and 1.2% 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), and 10% plasticizer BBSA (benzyl butyl sulfonamide).

[0129] Binder2-NoPlast = Composition based on 48.8% PA610 (tq defined elsewhere), 30% PA6 (tq defined elsewhere), and 20% EPR1 type impact modifier, and 1.2% organic stabilizers (consisting of 0.8% Lowinox 44B25 phenol from Great Lakes, 0.2% Irgafos 168 phosphite from Ciba, 0.2% Tinuvin 312 UV stabilizer from Ciba). EVOH = EVOH with 32% ethylene, type EVAL FP101B (Eval company) EVOH24 = EVOH with 24% ethylene, type EVAL M100B (Eval company) EVOHhi = EVOH with 27% ethylene and shock modified, type EVAL LA170B (Eval company) PPA10T / 6T = coPA10.T / 6.T with 40% mol of 6.T (of MFI 300°C, 5kg = 8, and melting T°C 280°C) + 15% EPR1 + stab orga EFEPc = Functionalized and conductive EFEP type Neoflon RP5000AS from Daikin Binder PA610 + PA6. Refers to a composition based on PA612 (of Mn 29000, and as defined elsewhere) and 36% of PA6 (of Mn 28000, and as defined elsewhere) and 1.2% of organic stabilizers (consisting of 0.8% of Lowinox 44B25 phenol from Great Lakes, 0.2% of Irgafos 168 phosphite from Ciba, 0.2% of Tinuvin 312 UV stabilizer from Ciba).

[0130] Structures with plasticizer-free layers located under the barrier and particularly in contact with the fluid show excellent results on the extractables test and much better than the counterexamples in which the layer in contact with the fluid is plasticized.

Claims

1. A multilayer tubular structure (MLT) for transporting fuels, in particular gasoline, especially alcohol-based gasoline, comprising, from the outside to the inside, at least one barrier layer (1) and at least one inner layer (2) located underneath the barrier layer, the barrier layer (1) being an EVOH comprising an impact modifier, said inner layer (2) or all of the layers (2) and any other layers located underneath the barrier layer, containing on average from 0 to 1.5% by weight of plasticizer relative respectively to the total weight of the composition of the layer (2) or to the total weight of all of the compositions of the layers (2) and any other layers located underneath the barrier layer, said outer layer (2) predominantly comprising at least one aliphatic polyamide or a polyamide consisting of more than 75% of aliphatic units, said aliphatic polyamide being selected from: - a polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA comprised from 4 to 7; - a polyamide denoted B and an average number of carbon atoms per nitrogen atom denoted CB comprised from 7.5 to 9.5; - a polyamide denoted C having an average number of carbon atoms per nitrogen atom denoted Cc comprised from 10 to 18; with the proviso that, when said inner layer (2) comprises at least three polyamides, at least one of said polyamides A, B or C is excluded, at least one layer further outward (3), located above the barrier layer, is present, said outer layer (3) predominantly comprising at least one aliphatic polyamide or a polyamide consisting of more than 75% of aliphatic units, in particular said aliphatic polyamide having an average number of carbon atoms per nitrogen atom of from 9.5 to 18, advantageously from 11 to 18, at least one second outer layer (3') located above the barrier layer is present, said layer (3') being located above the layer (3), said layer (3') being plasticized, said plasticizer being present in a proportion of 1.5% to 15% weight relative to the total weight of the composition of said layer, the thickness of said layer (3') preferably represents up to 20% of the total thickness of the tubular structure, in particular up to 200 mm, at least one layer (4) is present, said layer (4) containing not more than 15% by weight of plasticizer, preferably not more than 1.5% by weight of plasticizer, relative to the total weight of the components of layer (4), advantageously layer (4) is free of plasticizer, said layer (4) predominantly comprising at least one aliphatic polyamide or a polyamide consisting of more than 75% of aliphatic units, said aliphatic polyamide being selected from: - a polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA comprised from 4 to 7; - a polyamide denoted B and an average number of carbon atoms per nitrogen atom denoted CB comprised from 7.5 to 9.5, - a polyamide denoted C having an average number of carbon atoms per nitrogen atom denoted Cc comprised from 10 to 18; with the proviso that, when said layer (4) comprises at least three polyamides, at least one of said polyamides A, B or C is excluded, said layer (4) being located between the barrier layer (1) and the inner layer (2) and / or between the outer layer (3) and the barrier layer (1); or said layer (4) is a binder layer, the thickness of which is up to 15% of the structure (MLT).

2. The multilayer tubular structure (MLT) according to claim 1, wherein said inner layer (2) or each of the layers (2) and any other layers located underneath the barrier layer is (are) free of plasticizer.

3. The multilayer tubular structure (MLT) according to claim 1 or 2, wherein said outer layer (3) comprises from 0 to 15% of plasticizer relative to the total weight of the composition of layer (3), or wherein all the outer layers comprise on average from 0 to 5% of plasticizer.

4. The multilayer tubular structure (MLT) according to one of claims 1 to 3, wherein the layer (3') is the outermost layer and is the only plasticized layer, the layer(s) (3) being free of plasticizer.

5. The multilayer tubular structure (MLT) according to one of claims 1 to 4, wherein the polyamide of the inner layer (2) or the polyamide of the outer layer (3) is a fully aliphatic polyamide; preferably, the polyamide of the inner layer (2) and the polyamide of the outer layer (3) are fully aliphatic polyamides.

6. The multilayer tubular structure (MLT) according to one of claims 1 to 5, wherein the polyamide of the inner layer (2) is a composition based on a polyamide selected from A, B or C as defined in claim 1, in particular PA6, PA66, PA6 / 66, PA11, PA610, PA612, PA1012, the corresponding copolyamides and the mixtures of said polyamides or copolyamides, the polyamides obtained from a lactam advantageously being washed.

7. The multilayer tubular structure (MLT) according to one of claims 1 to 6, wherein the polyamide of the outer layer (3) is a polyamide selected from B or C as defined in claim 1, in particular PA11, PA12, PA610, PA612, PA1012, the corresponding copolyamides and the mixtures of said polyamides or copolyamides, the polyamides obtained from a lactam advantageously being washed.

8. The multilayer tubular structure (MLT) according to one of claims 1 to 7, wherein the polyamide of the inner layer (2) is a composition based on a polyamide selected from A, B or C as defined in claim 1, in particular PA6, PA66, PA6 / 66, PA11, PA610, PA612, PA1012, the corresponding copolyamides and the mixtures of said polyamides or copolyamides, the polyamides obtained from a lactam advantageously being washed, and the polyamide of the outer layer (3) is a polyamide selected from B or C as defined in claim 1, in particular PA11, PA12, PA610, PA612, PA1012, the corresponding copolyamides and the mixtures of said polyamides or copolyamides, the polyamides obtained from a lactam being advantageously washed.

9. The multilayer tubular structure (MLT) according to one of claims 1 to 8, wherein the polyamide of the inner layer (2) or of at least one of the other layers (2) is a conductive polyamide.

10. The multilayer tubular structure (MLT) according to one of claims 5 to 9, wherein the polyamide of layer (4) is selected from the binary mixtures: PA6 and PA12, PA6 and PA612, PA6 and PA610, PA12 and PA612, PA12 and PA610, PA1010 and PA612, PA1010 and PA610, PA1012 and PA612, PA1012 and PA610.

11. The multilayer tubular structure (MLT) according to one of claims 1 to 10, wherein at least one of the layers (2), (3), (3') and (4) comprises at least one impact modifier and / or at least one additive.

12. The use of a multilayer tubular structure (MLT) as defined in one of claims 1 to 11, for transporting fuels, in particular gasoline.