Multilayer structure based on recycled polyamide

Abstract

The present invention relates to a multilayer tubular structure (MLT) for transporting fluids for a motor vehicle, in particular air, oil, water, a urea solution, a glycol-based coolant, or a fuel such as gasoline, in particular alcohol-based gasoline, bio-gasoline or diesel, in particular bio-diesel, or hydrogen, said structure consisting of two layers: a layer (1) consisting of a composition predominantly comprising at least one semi-crystalline aliphatic polyamide, said composition consisting of at least 50% recycled material from a single-layer and / or multilayer tube that has been intended for transporting fluids for a motor vehicle, in particular as defined above, said tube consisting of a composition which predominantly comprises at least one polyamide, the tube having been subjected to different treatments selected from among grinding followed by re-compounding, and grinding followed by re-compounding and then reformulating for recycling purposes, simple grinding alone being excluded from the different treatments; a layer (2) consisting of a composition predominantly comprising at least one semi-crystalline aliphatic polyamide and optionally at least one impact modifier, and when the layer (2) consists of a composition predominantly comprising at least one semi-crystalline aliphatic polyamide that is PA12 and / or PA612 and / or PA1010, then said composition comprises said impact modifier, and said layer (2) consisting of at least 90% non-recycled material.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: MULTILAYER STRUCTURE BASED ON RECYCLED POLYAMIDE

[0003] Every year, several million motor vehicles become unusable worldwide. An end-of-life vehicle (ELV) contains numerous toxic and polluting products (liquid or solid): used oil, batteries, air conditioning fluid, explosive airbag components, etc. If handled improperly, this waste can lead to soil and water pollution, as well as accidents. ELVs are therefore considered hazardous waste.

[0004] A large number of vehicle components are salvageable and recyclable, in the form of used spare parts or raw materials. Parts intended for reuse (headlights, turn signals, engine, radiator, starter, hood, fenders, doors, etc.) are dismantled and stored for resale.

[0005] Non-recyclable carcasses and parts (ferrous and non-ferrous metals, plastics, glass, rubber, etc.) are crushed for recycling or landfill.

[0006] European Directive 2000 / 53 / EC on end-of-life vehicles has set a reuse and recovery rate of 95% by weight per vehicle from 2015.

[0007] Therefore, only 5% of ultimate waste should remain, i.e. waste which cannot be treated under the current technical and economic conditions and which will be incinerated or removed to specific storage centers.

[0008] The 95% reused and recovered are subject to:

[0009] Energy recovery: use of waste (oils, tires, plastics, etc.) as a means of energy production, by direct incineration with or without other waste;

[0010] Material recovery: Reuse or reuse: new use of a part which retains the same use and is not transformed, or Recycling: operation aimed at introducing materials from waste into the production cycle, in total or partial replacement of a virgin material.

[0011] A motor vehicle contains a large number of pipes, including pipes intended for the transport of fluids such as air, oil (for example for cooling the automatic gearbox "TOC, Transmission Oil Cooler), water, a urea solution, a glycol-based coolant, a fuel such as gasoline, in particular bio-gasoline or diesel, in particular biodiesel, or hydrogen.

[0012] These pipes can be single-layer and / or multi-layer tubular structures, in particular based on polyamide(s). When the motor vehicle is out of use, the various pipes present in it are generally very or too degraded to be able to be reused as such, in the form of a tube, without risk or without this leading to excessively degraded usage properties.

[0013] Indeed, the tubes, particularly under the engine hood, are placed in a severe thermo-oxidative environment due to the heat released by the engine, which can typically reach 150°C, and the presence of air and therefore oxygen. Each 10°C increase in temperature typically results in a halving of the tube's lifespan, as well as the degradation of certain additives in said tubes, such as stabilizers.

[0014] Furthermore, a fuel transport pipe, for example a polyamide pipe which contains a plasticizer, has lost most of its plasticizer when it reaches the end of its life and the polyamide initially present is depolymerized and / or degraded and has lost most of its stabilizers, which prevents its safe reuse.

[0015] Until now, the used automotive hose is not reused and is often incinerated, but this then contributes to global warming, the reduction of which is becoming one of the major challenges of the 21st century. ème century

[0016] Furthermore, several car manufacturers have the more or less long-term objective of recycling 100% of the vehicles they produce in order to achieve a zero environmental impact.

[0017] Therefore, the supply of recycled pipes to these manufacturers becomes essential and thus makes it possible to reduce the quantity of pipes to be thrown away or incinerated.

[0018] The present invention therefore relates to a multi-layer tubular structure (MLT) intended for the transport of automotive fluids, in particular air, oil, water, a urea solution, a glycol-based coolant, or a fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular bio-diesel, or hydrogen, consisting of two layers: a layer (1) consisting of a composition comprising mainly at least one semi-crystalline aliphatic polyamide, said composition being made up of at least 50% recycled material originating from a single-layer and / or multi-layer tube having been intended for the transport of automotive fluids, in particular as defined above, said tube being made up of a composition which mainly comprises at least one polyamide, said tube having undergone various treatments chosen from grinding then recompounding,and grinding then recompounding and then reformulation to be able to be recycled, a simple single grinding being excluded from the different treatments, a layer (2) consisting of a composition comprising mainly at least one semi-crystalline aliphatic polyamide and optionally at least one impact modifier, and when the layer (2) consists of a composition comprising mainly at least one semi-crystalline aliphatic polyamide which is PA12 or PA612 or PA1010, then said composition comprises said impact modifier, and said layer (2) being made of at least 90% of non-recycled material.,

[0019] The inventors have therefore surprisingly found that a polyamide-based layer consisting of at least 50% recycled material, in contact with a polyamide layer consisting of non-recycled material, allows the formation of a multilayer tubular structure capable of transporting an automotive fluid, in particular air, oil, water, a urea solution, a glycol-based coolant, or a fuel such as gasoline, in particular bio-gasoline or diesel, in particular bio-diesel, or hydrogen, regardless of the type of fluid initially transported by the recycled single-layer and / or multilayer tube constituting the layer in contact with the transported fluid, said multilayer structure unexpectedly exhibiting much better properties than those of the same tubular structure whose polyamide-based layer (1) consisting of at least 50% recycled material is of simply ground origin.

[0020] When using tubes for transporting or storing fluids in motor vehicles, new species resulting from oxidation mechanisms, in particular amide functions and / or methylene alpha to said amide functions, such as imide functions, carboxylic acids, primary amides and alcohols appear in the polyamides constituting said tubes or reservoirs. Said functions can be detected by infrared spectrometry.

[0021] Thus the absorption band from 1700 to 1740cm -1 corresponds to an imide, that of 1680 to 1720 cm -1 to the carbonyl of the carboxylic acid and that from 3580 to 3670 cm-1 corresponds to the alcohol function of the carboxylic acid.

[0022] The absorption band from 3580 to 3670 cm-1 corresponds to the free alcohol function.

[0023] The amide function is characterized on the one hand by a pair of absorption bands from 3100 to 3500 cm-1 and from 15560 to 1640 cm-1 which corresponds to the NH group of the amide and on the other hand by the absorption band from 1650 to 1700 cm-1 which corresponds to the carbonyl group of the amide.

[0024] In one embodiment, said polyamide of said single-layer and / or multi-layer tube having been intended for the transport of automobile fluids, or still used, has functions resulting from oxidation reactions chosen from imide functions, carboxylic acids, alcohols and their mixtures, in a molar ratio relative to the amide functions greater than that of the same polyamide constituting an unused tube having never before transported automobile fluids.

[0025] Advantageously, said molar ratio of the functions resulting from oxidation reactions is between 1 / 10000 and 1 / 20.

[0026] Concentrations can be measured by proton NMR in dichloromethane-d2, adding HFIP (hexafluoroisopropanol) to solubilize the polyamide.

[0027] In a first variant, said molar ratio of imide functions is from 1 / 1000 to 1 / 20, in particular from 1 / 500 to 1 / 20, in particular from 1 / 200 to 1 / 50.

[0028] In a second variant, said molar ratio of carboxylic acid functions is from 1 / 5000 to 1 / 20, in particular from 1 / 3000 to 1 / 25, very advantageously from 1 / 500 to 1 / 50.

[0029] In a third variant, said molar ratio of alcohol functions is from 1 / 1000 to 1 / 20 and advantageously from 1 / 1000 to 1 / 25, very advantageously from 1 / 200 to 1 / 50.

[0030] In one embodiment, said tubular structure presents during the first storage of gasoline, in particular alcoholic gasoline, at most 0.3 g / m2 of insoluble extract, advantageously at most 0.2 g / m 2 .

[0031] In one embodiment, said tubular structure has, during the first storage of gasoline, in particular alcoholic gasoline, 30%, in particular 40%, in particular 50% less insoluble extract than the same tubular structure made from non-recycled material.

[0032] The single-layer tubular structure intended for the transport of fluids for motor vehicles of the invention makes it possible to significantly reduce the proportion of extractables as determined by a test which consists of filling a tubular structure with FAM-B type alcoholic gasoline and heating the assembly to 60°C for 96 hours, then emptying it by filtering the fluid into a beaker.

[0033] The insoluble extracts present during filtration on the filter are weighed after drying and represent less than 0.3 g / m2.

[0034] The soluble extracts are quantified by allowing the beaker filtrate to evaporate at room temperature and then weighing this residue. The proportion of soluble extracts is advantageously less than or equal to approximately 15g / m2 of internal tube surface area.

[0035] Said tubular structure has a lower extractable content than that of the same tubular structure made from non-recycled material, i.e. virgin or original material during the first storage of gasoline, in particular alcoholic gasoline, and in particular a proportion of insoluble extract lower by 30%, in particular 40%, in particular 50% compared to the proportion present in the same tubular structure but made from non-recycled or virgin material.

[0036] The tubular structure also advantageously comprises stabilizer residues chosen from phenols, quinones, stylbenequinone and phosphite.

[0037] The recycled polyamide advantageously comprises alkyl chain ends with a carbon number, from 1 to 18, higher than that of a virgin PA.

[0038] Advantageously, the chain end rate is between 1 ppm and 0.5% as determined by NMR or potentiometry.

[0039] Used polyamide (to be recycled) is more crystalline than virgin polyamide.

[0040] The percentage of crystallization can be measured by DSC (or by X-ray).

[0041] Advantageously, the used polyamide has a crystallinity level of at least 2%, in particular at least 5% higher than that of a virgin polyamide as measured by DSC. The term "fluid" designates a gas or a liquid used in the automobile, in particular air, oil, water, a urea solution, a glycol-based coolant, or a fuel such as gasoline, in particular alcohol-based gasoline, bio-gasoline or diesel, in particular bio-diesel, or hydrogen.

[0042] Advantageously, said fluid designates fuels, in particular gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular biodiesel.

[0043] 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.

[0044] 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.

[0045] The term “polyamide-based” means at least 50% by weight of polyamide in the layer.

[0046] The expression “a composition comprising predominantly at least one polyamide...” means at least 50% by weight of said polyamide in the composition.

[0047] In one embodiment, said layer (2) consists of a composition comprising predominantly at least one semi-crystalline aliphatic polyamide and at least one impact modifier in a proportion of 3 to 45% by weight relative to the total weight of the composition. With regard to layer (1)

[0048] The layer (1) is made up of a composition comprising mainly at least one semi-crystalline aliphatic polyamide, said composition being made up of at least 50% recycled material originating from a single-layer and / or multi-layer tube intended for the transport of automobile fluids.

[0049] The nomenclature used to define polyamides is described in ISO 1874-1:201 1 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation" and is well known to those skilled in the art.

[0050] The term “polyamide” according to the invention designates both a homopolyamide and a copolyamide.

[0051] The expression "semi-crystalline polyamide" within the meaning of the invention throughout the description designates polyamides which have a melting temperature (Tf) and an enthalpy of fusion AH > 25 J / g, in particular > 40 J / g, in particular > 45 J / g, as well as a glass transition temperature (Tg) as determined by DSC according to ISO 11357-1:2016 and ISO 11357-2 and 3:2013, at a heating rate of 20K / min.

[0052] Said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one lactam, or from the polycondensation of at least one amino acid, or from the polycondensation of at least one diamine Xa with at least one dicarboxylic acid Yb.

[0053] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one lactam, said at least one lactam may be chosen from a C6 to C18 lactam, preferably a C10 to C18 lactam, more preferably a C10 to C12 lactam. A C6 to C12 lactam is in particular caprolactam, decanolactam, undecanolactam, and lauryllactam.

[0054] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one lactam, it can therefore comprise a single lactam or several lactams.

[0055] Advantageously, said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of a single lactam and said lactam is chosen from lauryllactam and undecanolactam, advantageously lauryllactam.

[0056] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one amino acid, said at least one amino acid may be chosen from a C6 to C18 amino acid, preferably a C10 to C18 amino acid, more preferably a C10 to C12 amino acid. A C6 to C12 amino acid is in particular 6-aminohexanoic acid, 9-aminononanoic acid, 10-aminodecanoic acid, 10-aminoundecanoic acid, 12-aminododecanoic acid and 11-aminoundecanoic acid as well as its derivatives, in particular N-heptyl-11-aminoundecanoic acid.

[0057] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one amino acid, it can therefore comprise a single amino acid or several amino acids.

[0058] Advantageously, said aliphatic semi-crystalline polyamide is obtained from the polycondensation of a single amino acid and said amino acid is chosen from 11-aminoundecanoic acid and 12-aminododecanoic acid, advantageously 11-aminoundecanoic acid.

[0059] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one C4-C36, preferably C5-C18, preferably C5-C12, more preferably C10-C12, diamine Xa with at least one C4-C36, preferably C6-C18, preferably C6-C12, more preferably C10-C12, diacid Yb, then said at least one Xa diamine is an aliphatic diamine and said at least one Yb diacid is an aliphatic diacid.

[0060] The diamine can be linear or branched. Advantageously, it is linear.

[0061] Said at least one C4-C36 diamine Xa may in particular be chosen from 1,4-butanediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylediamine, 1,8-octamethylediamine, 1,9-nonamethylediamine, 1,10-decamethylediamine, 1,11-undecamethylediamine, 1,12-dodecamethylediamine, 1,13-tridecamethylediamine, 1,14-tetradecamethylediamine, 1,16-hexadecamethylediamine and 1,18-octadecamethylediamine, octadecenediamine, eicosanediamine, docosanediamine and diamines obtained from fatty acids.Advantageously, said at least one diamine Xa is C5-C18 and chosen from 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethyldiamine, 1,8-octamethyldiamine, 1,9-nonamethyldiamine, 1,10-decamethyldiamine, 1,11-undecamethyldiamine, 1,12-dodecamethyldiamine, 1,13-tridecamethyldiamine, 1,14-tetradecamethyldiamine, 1,16-hexadecamethyldiamine and 1,18-octadecamethyldiamine.

[0062] Advantageously, said at least one diamine Xa in C5 to C12 is in particular chosen from 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylediamine, 1,8-octamethylediamine, 1,9-nonamethylediamine, 1,10-decamethylediamine, 1,11-undecamethylediamine, 1,12-dodecamethylediamine. Advantageously, said at least one diamine Xa in C6 to C12 is in particular chosen from 1,6-hexamethylenediamine, 1,7-heptamethyldiamine, 1,8-octamethyldiamine, 1,9-nonamethyldiamine, 1,10-decamethyldiamine, 1,11-undecamethyldiamine, 1,12-dodecamethyldiamine.

[0063] Advantageously, the diamine Xa used is C10 to C12, in particular chosen from 1,10-decamethyldiamine, 1,11-undecamethyldiamine, 1,12-dodecamethyldiamine.

[0064] Said at least one C4 to C36 dicarboxylic acid Yb may be chosen from succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, and diacids obtained from fatty acids.

[0065] The diacid can be linear or branched. Advantageously, it is linear.

[0066] Advantageously, said at least one dicarboxylic acid Yb is C6 to C18 and is chosen from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid.

[0067] Advantageously, said at least one dicarboxylic acid Yb is C6 to C12 and is chosen from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid.

[0068] Advantageously, said at least one dicarboxylic acid Yb is C10 to C12 and is chosen from sebacic acid, undecanedioic acid, dodecanedioic acid.

[0069] When said aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one diamine Xa with at least one dicarboxylic acid Yb, it can therefore comprise a single diamine or several diamines and a single dicarboxylic acid or several dicarboxylic acids.

[0070] Advantageously, said aliphatic semi-crystalline polyamide is obtained from the polycondensation of a single diamine Xa with a single dicarboxylic acid Yb. The expression "predominantly comprising at least one aliphatic type polyamide" means that said composition of the layer (1) comprises at least 50% by weight of at least one aliphatic polyamide relative to the total weight of said composition. Advantageously, said composition of the layer (1) comprises at least 60% by weight, in particular at least 70% by weight, in particular at least 80% by weight, more particularly at least 90% by weight of at least one aliphatic polyamide relative to the total weight of said composition.

[0071] Said composition of the layer (1) is made up of at least 50% recycled material from a single-layer and / or multi-layer tube intended for the transport of automobile fluids.

[0072] This means either that the “at least one majority polyamide” of said composition corresponds in its entirety to what is called “at least 50% recycled material” or that at least 50% by weight of all the constituents of the composition are of recycled origin from single-layer tube, or multi-layer tube, or a mixture of single-layer and multi-layer tube.

[0073] The recycled material may come from a single-layer and / or multi-layer tube, said single-layer and / or multi-layer tubes having been intended for the transport of automotive fluid. Said tube is therefore a used tube, that is to say that it has been used for at least one year for the transport of said fluid defined above. Said single-layer tube is made of a composition comprising a semi-crystalline aliphatic polyamide and optionally impact modifiers and / or additives and / or plasticizers and / or antistatic fillers.

[0074] Said multilayer tube comprises at least one layer consisting of a composition comprising a semi-crystalline aliphatic polyamide and optionally impact modifiers and / or additives. It may therefore comprise other layers consisting of a thermoplastic polymer other than a semi-crystalline aliphatic polyamide, such as for example a polypropylene, a semi-aromatic polyamide or a poly ethylene vinyl alcohol (EVOH).

[0075] It is obvious that the single-layer tube can also be a mixture of single-layer tubes, that is to say for example two types of single-layer tubes each made of a different semi-crystalline aliphatic polyamide, for example a PA1 1 and a PA12.

[0076] It is also obvious that the multilayer tube can also be a mixture of different types of multilayer tube, provided that at least one of the layers of one of the types of multilayer tube is made of a semi-crystalline aliphatic polyamide.

[0077] If the mixed tubes are incompatible with each other, then the addition of a second semi-crystalline aliphatic polyamide noted B and having an average number of carbon atoms per nitrogen atom noted CB = Ce - 1, preferably CB = Ce - 2 and preferably a third polyamide makes it possible to make them compatible.

[0078] Said single-layer and / or multi-layer tube which was intended for the transport of automobile fluid and which is therefore used can undergo several different treatments in order to be recycled:

[0079] It can be ground and recompounded, that is to say that after grinding, the ground particles are fed into an extruder, in particular of the co-rotating twin-screw type, or of the co-kneader type (Buss), where they are remixed by melting. The molten material comes out of the extruder in rods which are cooled and cut into granules;

[0080] It can be ground and recompounded and reformulated, that is to say that after grinding, the ground particles are fed into an extruder, as defined above where they are remixed by melting with the addition of at least one compound chosen from a semi-crystalline aliphatic polyamide, of recycled origin or not, at least one impact modifier, a plasticizer, an additive and antistatic fillers. The molten material emerges from the extruder in rods which are cooled and cut into granules.

[0081] A simply crushed tube is therefore excluded from said used single-layer and / or multi-layer tube and which was intended for the transport of automotive fluid.

[0082] Optionally, the single-layer and / or multi-layer tube intended for the transport of automotive fluid undergoes a washing and / or cleaning step before crushing.

[0083] Optionally, the crushed tube undergoes a washing and / or cleaning step after crushing. Optionally, the single-layer and / or multi-layer tube that was intended for the transport of automotive fluid undergoes a washing and / or cleaning step before crushing and is then crushed and optionally undergoes, before recompounding, a washing and / or cleaning step after crushing.

[0084] The cleaning step can be carried out, for example, under vacuum.

[0085] In one embodiment, said composition of the layer (1) comprises: at least 50% by weight, in particular from 50% to 99% by weight, in particular from 50% to 98% by weight, of at least one semi-crystalline aliphatic polyamide denoted C having an average number of carbon atoms per nitrogen atom denoted Ce of from 6 to 18, advantageously from 8 to 12; from 0 to 50% by weight of at least one semi-crystalline aliphatic polyamide denoted B and having an average number of carbon atoms per nitrogen atom denoted CB = Ce - 1, preferably CB = Ce - 2; from 0 to 50% by weight of a semi-crystalline aliphatic polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA = CB - 1, preferably CA = CB - 2;from 0 to 45% by weight of at least one impact modifier, in particular from 1 to 45% by weight of at least one impact modifier, in particular from 2 to 45% by weight of at least one impact modifier, from 0 to 20% by weight of at least one plasticizer, from 0 to 2% by weight of at least one additive, the sum of the constituents being equal to 100%.;

[0086] In another embodiment, said composition of the layer (1) consists of: at least 50% by weight, in particular from 50% to 99% by weight, in particular from 50% to 98% by weight, of at least one semi-crystalline aliphatic polyamide denoted C having an average number of carbon atoms per nitrogen atom denoted Ce of from 6 to 18, advantageously from 8 to 12; from 0 to 25% by weight of at least one semi-crystalline aliphatic polyamide denoted B and having an average number of carbon atoms per nitrogen atom denoted CB = Ce - 1, preferably CB = Ce - 2; from 0 to 25% by weight of a semi-crystalline aliphatic polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA = CB - 1, preferably CA = CB - 2;from 0 to 45% by weight of at least one impact modifier, in particular from 1 to 45% by weight of at least one impact modifier, in particular from 2 to 45% by weight of at least one impact modifier, from 0 to 20% of at least one plasticizer, from 0 to 2% by weight of at least one additive, the sum of the constituents being equal to 100%.;

[0087] In yet another embodiment, said composition of the layer (1) comprises: at least 50% by weight, in particular from 50% to 97% by weight, of at least one semi-crystalline aliphatic polyamide denoted C having an average number of carbon atoms per nitrogen atom denoted Ce of from 6 to 18, advantageously from 8 to 12; from 0 to 25% by weight of at least one semi-crystalline aliphatic polyamide denoted B and having an average number of carbon atoms per nitrogen atom denoted CB = Ce - 1, preferably CB = Ce - 2; from 0 to 25% by weight of a semi-crystalline aliphatic polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA = CB - 1, preferably CA = CB - 2; from 0 to 45% by weight of at least one impact modifier, in particular from 3 to 45% by weight of at least one impact modifier, from 0 to 20% by weight of at least one plasticizer, from 0 to 2% by weight of at least one additive, the sum of the constituents being equal to 100%.

[0088] Polyamides rated A, B and C may be of recycled or non-recycled origin provided that the composition of the layer (1) is made up of at least 50% recycled material.

[0089] Advantageously, the Tf of the majority aliphatic semi-crystalline polyamide of the layer (1) is <225°C, in particular^ 200°C, as determined according to ISO 11357-3: 2013, at a heating rate of 20K / min.

[0090] Advantageously, the majority of the aliphatic semi-crystalline polyamide in layer (1) has a crystallization enthalpy > 25 J / g, preferably > 40 J / g, in particular > 45 J / g as determined by DSC according to standard ISO 11357-3:2013, at a heating rate of 20K / min.

[0091] In one embodiment, the recycled material is from a single-layer and / or multi-layer tube selected from a crushed and recompounded single-layer and / or multi-layer tube, and a crushed, recompounded and reformulated single-layer and / or multi-layer tube.

[0092] Advantageously, in this embodiment, said composition of the layer (1) is free of plasticizer and / or impact modifier and said recycled material comes from a single-layer and / or multi-layer tube chosen from a crushed and recompounded single-layer and / or multi-layer tube, and a crushed, recompounded and reformulated single-layer and / or multi-layer tube.

[0093] In one embodiment, said composition of the layer (1) is free of plasticizer and / or impact modifier and said recycled material comes from a tube chosen from a crushed and recompounded tube and a crushed, recompounded and reformulated tube.

[0094] In another embodiment, said composition of the layer (1) comprises at least one compound chosen from plasticizer, an impact modifier and an additive, and said recycled material is chosen from a crushed tube, then recompounded and reformulated.

[0095] Advantageously, in these last two embodiments, said tube is a single-layer tube and / or a multi-layer tube. In one embodiment, the fluid transported by said single-layer and / or multi-layer tube is different from that of said multi-layer tubular structure (MLT).

[0096] This means that if the single-layer and / or multi-layer tube has transported a fluid such as air, said multi-layer tubular structure (MLT) may be intended to transport gasoline or, if the single-layer and / or multi-layer tube has transported a fluid such as alcoholic gasoline, said tubular structure (MLT) may be intended to transport diesel.

[0097] In another embodiment, the fluid transported by said single-layer and / or multi-layer tube is the same as that of said multi-layer tubular (MLT) structure.

[0098] This means that if the single-layer and / or multi-layer tube has transported a fluid such as gasoline, said tubular structure (MLT) may be intended to transport gasoline provided that the gasoline of the single-layer and / or multi-layer tube and of said multi-layer tubular structure (MLT) is the same, for example, alcoholic gasoline. Advantageously, the recycled material comes from a single-layer tube made of a composition comprising only a PA11.

[0099] In one embodiment, said composition of the layer (1) comprises at least 60% by weight, in particular at least 70% by weight, in particular at least 80% by weight, in particular at least 90% by weight, more particularly at least 95% of recycled material.

[0100] In another embodiment, said composition of the layer (1) consists of 100% by weight of recycled material.

[0101] Recycled used single-layer or multi-layer tube

[0102] In a first variant, said tube which was intended for the transport of fluid for automobiles is single-layer or multi-layer, ground and recompounded and the composition of the layer (1) resulting from said recycling is made up of: at least 61% by weight, in particular from 96% to 99% by weight, in particular from 96% to 98% by weight, of at least one semi-crystalline aliphatic polyamide noted C having an average number of carbon atoms per nitrogen atom noted Ce of from 6 to 18, advantageously from 8 to 12; from 0 to 2% of at least one plasticizer, from 0 to 2% by weight of at least one additive, in particular a stabilizer; the sum of the constituents being equal to 100%.

[0103] Advantageously, in this first variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11. Advantageously in this first variant, said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular bio-diesel.

[0104] Advantageously, in this first variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11 and said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular biodiesel.

[0105] Advantageously, said tube which was intended for the transport of fluid for automobiles is single-layer.

[0106] In a second variant, said tube which was intended for the transport of fluid for automobiles is single-layer or multi-layer, ground, recompounded and reformulated and the composition of the layer (1) resulting from said recycling and reformulated is made up of: at least 58.5% by weight of at least one semi-crystalline aliphatic polyamide noted C having an average number of carbon atoms per nitrogen atom noted Ce of from 6 to 18, advantageously from 8 to 12; from 6 to 14% of at least one plasticizer, in particular from 6 to 8%; from 0.5 to 1.5% by weight of at least one additive, in particular a stabilizer; the sum of the constituents being equal to 100%.

[0107] Advantageously, in this second variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11.

[0108] Advantageously in this second variant, said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular bio-diesel.

[0109] Advantageously, in this second variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11 and said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular biodiesel.

[0110] Advantageously, said tube which was intended for the transport of fluid for automobiles is single-layer.

[0111] In a third variant, said tube which was intended for the transport of fluid for automobiles is single-layer or multi-layer, ground, recompounded and reformulated and the composition of the layer (1) resulting from said recycling and reformulated is made up of: at least 58% by weight of at least one semi-crystalline aliphatic polyamide noted C having an average number of carbon atoms per nitrogen atom noted Ce of from 6 to 18, advantageously from 8 to 12; from 6 to 14% of at least one plasticizer, in particular from 6 to 8%; from 1 to 2% by weight of at least one additive, in particular a stabilizer and a catalyst; the sum of the constituents being equal to 100%.

[0112] Advantageously, in this third variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11.

[0113] Advantageously in this third variant, said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular bio-diesel.

[0114] Advantageously, in this third variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11 and said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular biodiesel.

[0115] Advantageously, said tube which was intended for the transport of fluid for automobiles is single-layer.

[0116] Advantageously, the composition is degassed during compounding, even more advantageously the degassing is located just after the melting zone, and before the zone of introduction of plasticizer such as BBSA or other.

[0117] In a fourth variant, said tube which was intended for the transport of fluid for automobiles is single-layer or multi-layer, ground, recompounded and reformulated and the composition of the layer (1) resulting from said recycling and reformulated is made up of: at least 50% by weight, in particular from 50% to 99% by weight, in particular from 50% to 98% by weight, of at least one semi-crystalline aliphatic polyamide noted C having an average number of carbon atoms per nitrogen atom noted Ce of from 6 to 18, advantageously from 8 to 12; from 0 to 25% by weight of at least one semi-crystalline aliphatic polyamide noted B and having an average number of carbon atoms per nitrogen atom noted CB = Ce - 1, preferably CB = Ce - 2; from 0 to 25% by weight of a semi-crystalline aliphatic polyamide noted A having an average number of carbon atoms per nitrogen atom noted CA = CB - 1, preferably CA = CB - 2;from 0 to 2% of at least one plasticizer, from 0 to 2% by weight of at least one additive, the sum of the constituents being equal to 100%.;

[0118] Advantageously, in this fourth variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11.

[0119] Advantageously in this fourth variant, said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular bio-diesel.

[0120] Advantageously, in this fourth variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11 and said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular biodiesel.

[0121] Advantageously, said tube which was intended for the transport of fluid for automobiles is single-layer.

[0122] In a fifth variant, said tube which was intended for the transport of fluid for automobiles is single-layer or multi-layer, ground, recompounded and reformulated and the composition of the layer (1) resulting from said recycling and reformulated is made up of: at least 55% by weight, in particular from 55% to 99% by weight, in particular from 55% to 98% by weight, of at least one semi-crystalline aliphatic polyamide noted C having an average number of carbon atoms per nitrogen atom noted Ce of from 6 to 18, advantageously from 8 to 12; from 0 to 45% by weight of at least one impact modifier, in particular from 1 to 45% by weight of at least one impact modifier, in particular from 2 to 45% by weight of at least one impact modifier, the sum of the constituents being equal to 100%.

[0123] Advantageously, in this fifth variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11.

[0124] Advantageously in this fifth variant, said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular bio-diesel.

[0125] Advantageously, in this fifth variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11 and said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular biodiesel.

[0126] Advantageously, said tube which was intended for the transport of fluid for automobiles is single-layer.

[0127] In a sixth variant, said tube which was intended for the transport of fluid for automobiles is single-layer or multi-layer, ground, recompounded and reformulated and the composition of the layer (1) resulting from said recycling and reformulated is made up of: at least 50% by weight of at least one semi-crystalline aliphatic polyamide noted C having an average number of carbon atoms per nitrogen atom noted Ce of from 6 to 18, advantageously from 8 to 12; from 0 to 43.5% by weight of at least one impact modifier, in particular from 1 to 43.5% by weight of at least one impact modifier, in particular from 2 to 43.5% by weight of at least one impact modifier, from 6 to 14% of at least one plasticizer, in particular from 6 to 8%; from 0.5 to 1.5% by weight of at least one additive, in particular a stabilizer; the sum of the constituents being equal to 100%.

[0128] Advantageously, in this sixth variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11.

[0129] Advantageously in this sixth variant, said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular bio-diesel.

[0130] Advantageously, in this sixth variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11 and said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular biodiesel.

[0131] Advantageously, said tube which was intended for the transport of fluid for automobiles is single-layer.

[0132] In a seventh variant, said tube which was intended for the transport of fluid for automobiles is single-layer or multi-layer, ground, recompounded and reformulated and the composition of the layer (1) resulting from said recycling and reformulated is made up of: at least 50% by weight of at least one semi-crystalline aliphatic polyamide noted C having an average number of carbon atoms per nitrogen atom noted Ce of from 6 to 18, advantageously from 8 to 12; from 0 to 43% by weight of at least one impact modifier, in particular from 1 to 43% by weight of at least one impact modifier, in particular from 2 to 38% by weight of at least one impact modifier, from 6 to 14% of at least one plasticizer, in particular from 6 to 8%; from 1 to 2% by weight of at least one additive, in particular a stabilizer and a catalyst; the sum of the constituents being equal to 100%.

[0133] Advantageously, in this seventh variant, the semi-crystalline aliphatic polyamide noted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11.

[0134] Advantageously in this seventh variant, said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular bio-diesel.

[0135] Advantageously, in this seventh variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11 and said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular biodiesel.

[0136] Advantageously, said tube which was intended for the transport of fluid for automobiles is single-layer.

[0137] In an eighth variant, said tube which was intended for the transport of fluid for automobiles is single-layer or multi-layer, ground, recompounded and reformulated and the composition of the layer (1) resulting from said recycling and reformulated is made up of: at least 50% by weight of at least one semi-crystalline aliphatic polyamide noted C having an average number of carbon atoms per nitrogen atom noted Ce of from 6 to 18, advantageously of from 8 to 12; from 0 to 25% by weight of at least one semi-crystalline aliphatic polyamide noted B and having an average number of carbon atoms per nitrogen atom noted CB = Ce - 1, preferably CB = Ce - 2; from 0 to 25% by weight of a semi-crystalline aliphatic polyamide noted A having an average number of carbon atoms per nitrogen atom noted CA = CB - 1, preferably CA = CB - 2;from 0 to 43% by weight of at least one impact modifier, in particular from 1 to 43% by weight of at least one impact modifier, in particular from 2 to 38% by weight of at least one impact modifier, from 0 to 20% of at least one plasticizer, from 0 to 2% by weight of at least one additive, the sum of the constituents being equal to 100%.;

[0138] Advantageously, in this eighth variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11.

[0139] Advantageously in this eighth variant, said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular bio-diesel.

[0140] Advantageously, in this eighth variant, the semi-crystalline aliphatic polyamide denoted C is chosen from PA612, PA1012, PA1010, PA11 and PA12, in particular PA11 and said tube was intended for the transport of fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular biodiesel.

[0141] Advantageously, said tube which was intended for the transport of fluid for automobiles is single-layer.

[0142] Regarding the shock modifier

[0143] The impact modifier is advantageously made up of a polymer having a flexural modulus of less than 100 MPa measured according to standard ISO 178: 2010, determined at 23°C with a relative humidity: RH50%, and a Tg of less than 0°C (measured according to standard 11357-2: 2013 at the inflection point of the DSC thermogram, at a heating rate of 20K / min), in particular a polyolefin.

[0144] 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. For simplicity, the polyolefin has been designated (B) and functionalized polyolefins (B1) and non-functionalized polyolefins (B2) have been described below.

[0145] A non-functionalized polyolefin (B2) is typically a homopolymer or copolymer of alpha olefins or diolefins, such as, for example, ethylene, propylene, butene-1, octene-1, butadiene. Examples include:

[0146] - homopolymers and copolymers of polyethylene, in particular LDPE, HDPE, LLDPE (linear low density polyethylene), VLDPE (very low density polyethylene) and metallocene polyethylene.

[0147] - homopolymers or copolymers of propylene.

[0148] - ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (abbreviation for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM). styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS) block copolymers.

[0149] - copolymers of ethylene with at least one product chosen from salts or esters of unsaturated carboxylic acids such as alkyl (meth)acrylate (for example methyl acrylate), or vinyl esters of saturated carboxylic acids such as vinyl acetate (EVA), the proportion of comonomer being able to reach 40% by weight.

[0150] The functionalized polyolefin (B1) may be a polymer of alpha olefins having reactive units (the functionalities); such reactive units are acid, anhydride, or epoxy functions. As an example, mention may be made of the preceding polyolefins (B2) grafted or co- or terpolymerized by unsaturated epoxides such as glycidyl (meth)acrylate, or by carboxylic acids or the corresponding salts or esters such as (meth)acrylic acid (the latter being able to be neutralized totally or partially by metals such as Zn, etc.) or even by carboxylic acid anhydrides such as maleic anhydride. A functionalized polyolefin is, for example, a PE / EPR blend, the weight ratio of which can vary widely, for example between 40 / 60 and 90 / 10, said blend being co-grafted with an anhydride, in particular maleic anhydride, according to a grafting rate of, for example, 0.01 to 5% by weight.

[0151] The functionalized polyolefin (B1) can be chosen from the following (co)polymers, grafted with maleic anhydride or glycidyl methacrylate, in which the grafting rate is for example from 0.01 to 5% by weight:

[0152] - PE, PP, copolymers of ethylene with propylene, butene, hexene, or octene containing for example 35 to 80% by weight of ethylene;

[0153] - ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (abbreviation for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM). styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS) block copolymers.

[0154] - ethylene and vinyl acetate (EVA) copolymers, containing up to 40% by weight of vinyl acetate; - ethylene and alkyl (meth)acrylate copolymers, containing up to 40% by weight of alkyl (meth)acrylate;

[0155] - ethylene vinyl acetate (EVA) and alkyl (meth)acrylate copolymers, containing up to 40% by weight of comonomers.

[0156] The functionalized polyolefin (B1) can also be chosen from ethylene / propylene copolymers with a majority of propylene grafted with maleic anhydride then condensed with mono-amine polyamide (or a polyamide oligomer) (products described in EP-A-0342066).

[0157] The functionalized polyolefin (B1) may also be a co- or terpolymer of at least the following units: (1) ethylene, (2) alkyl (meth)acrylate or saturated carboxylic acid vinyl ester and (3) anhydride such as maleic anhydride or (meth)acrylic acid or epoxy such as glycidyl (meth)acrylate.

[0158] As examples of functionalized polyolefins of the latter type, the following copolymers may be mentioned, where ethylene preferably represents at least 60% by weight and where the ter monomer (the function) represents, for example, from 0.1 to 10% by weight of the copolymer:

[0159] - ethylene / alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers;

[0160] - ethylene / vinyl acetate / maleic anhydride or glycidyl methacrylate copolymers;

[0161] - ethylene / vinyl acetate or alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers.

[0162] In the above copolymers, (meth)acrylic acid can be salified with Zn or Li.

[0163] The term "alkyl (meth)acrylate" in (B1) or (B2) means C1-C8 alkyl methacrylates and acrylates, and may be selected from methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate.

[0164] Furthermore, the aforementioned polyolefins (B1) can also be crosslinked by any suitable process or agent (diepoxy, diacid, peroxide, etc.); the term functionalized polyolefin also includes mixtures of the aforementioned polyolefins with a difunctional reagent such as diacid, dianhydride, diepoxy, etc. capable of reacting with them or mixtures of at least two functionalized polyolefins capable of reacting with each other.

[0165] The above-mentioned copolymers, (B1) and (B2), can be copolymerized in a statistical or block manner and have a linear or branched structure. The molecular weight, the MFI index, the density of these polyolefins can also vary to a large extent, which will be appreciated by those skilled in the art. MFI, abbreviation of Melt Flow Index, is the melt flow index. It is measured according to ASTM 1238.

[0166] Advantageously, the non-functionalized polyolefins (B2) are chosen from homopolymers or copolymers of polypropylene and any homopolymer of ethylene or copolymer of ethylene and a comonomer of higher alpha olefin type such as butene, hexene, octene or 4-methyl 1-pentene. Examples that may be mentioned are PP, high density PE, medium density PE, linear low density PE, low density PE, very low density PE. These polyethylenes are known to those skilled in the art as being produced according to a “radical” process, according to a “Ziegler” type catalysis or, more recently, according to a so-called “metallocene” catalysis.

[0167] Advantageously, the functionalized polyolefins (B1) are chosen from any polymer comprising alpha olefinic units and units carrying polar reactive functions such as epoxy, carboxylic acid or carboxylic acid anhydride functions. Examples of such polymers include terpolymers of ethylene, alkyl acrylate and maleic anhydride or glycidyl methacrylate such as the Applicant's Lotader® or polyolefins grafted with maleic anhydride such as the Applicant's Orevac® as well as terpolymers of ethylene, alkyl acrylate and (meth)acrylic acid. Mention may also be made of homopolymers or copolymers of polypropylene grafted with a carboxylic acid anhydride and then condensed with polyamides or monoamine oligomers of polyamide.

[0168] Adding additives

[0169] The additives optionally used in the compositions of the invention are the conventional additives used in polyamides well known to those skilled in the art and are notably described in EP 2098580.

[0170] For example, they are selected from a catalyst, an antioxidant, a heat stabilizer, a UV absorber, a light stabilizer, a lubricant, an inorganic filler, a flame retardant, a nucleating agent and a colorant, reinforcing fibers, a wax and mixtures thereof.

[0171] The term "catalyst" refers to a polycondensation catalyst such as a mineral or organic acid.

[0172] Advantageously, the proportion by weight of catalyst is from about 50 ppm to about 5000 ppm, in particular from about 100 to about 3000 ppm relative to the total weight of the composition. Advantageously, the catalyst is chosen from phosphoric acid (H3PO4), phosphorous acid (H3PO3), hypophosphorous acid (H3PO2), or a mixture thereof.

[0173] For example, the stabilizer may be a UV stabilizer, an organic stabilizer or more generally a combination of organic stabilizers, such as a phenol-type antioxidant (for example of the type of irganox® 245 or 1098 or 1010 from Ciba-BASF), a phosphite-type antioxidant (for example irgafos® 126 and irgafos® 168 from Ciba-BASF) and possibly other stabilizers such as a HALS, which stands for Hindered Amine Light Stabilizer (for example Tinuvin® 770 from Ciba-BASF), a UV stabilizer (for example Tinuvin® 312 from Ciba) or a phosphorus-based stabilizer. It is also possible to use amine-type antioxidants such as Naugard® 445 from Crompton or polyfunctional stabilizers such as Nylostab® S-EED from Clariant.

[0174] This stabilizer can also be a mineral stabilizer, such as a copper-based stabilizer. Examples of such mineral stabilizers include copper halides and acetates. 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.

[0175] Regarding the plasticizer

[0176] The plasticizers are, for example, the plasticizers are selected from benzene sulfonamide derivatives, such as n-butyl benzene sulfonamide (BBSA); ethyl toluene sulfonamide or N-cyclohexyl toluene sulfonamide; esters of hydroxybenzoic acids, 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.

[0177] It would not be outside the scope of the invention to use a mixture of plasticizers.

[0178] The additives when present in the composition are advantageously present from 1 to 20% by weight, in particular from 5 to 15% by weight, in particular from 5 to 12% by weight.

[0179] Regarding antistatic charges

[0180] The antistatic fillers are for example chosen from carbon black, graphite, carbon fibers, carbon nanotubes, in particular carbon black and carbon nanotubes, As regards layer (2)

[0181] The terms “semi-crystalline polyamide” and “aliphatic” have the same definition as for layer (1).

[0182] Said at least one aliphatic semi-crystalline polyamide is obtained in the same manner as described above for layer (1).

[0183] In a first variant of the layer (2), said layer (2) is devoid of shock modifier.

[0184] In this case, the semi-crystalline aliphatic polyamide which is PA12 and / or PA612 and / or PA1010 is excluded from the composition which constitutes layer (2).

[0185] In a second variant of the layer (2), said layer (2) comprises from 3 to 45% by weight of at least one impact modifier, in particular from 5 to 20% by weight of at least one impact modifier.

[0186] In an embodiment of this second variant, said layer (2) is made up of a composition comprising: at least 50% by weight, in particular from 50% to 97% by weight, in particular from 50% to 95% by weight, of at least one semi-crystalline aliphatic polyamide denoted D having an average number of carbon atoms per nitrogen atom denoted CD of from 6 to 18, advantageously from 9 to 15; from 0 to 25% by weight of at least one semi-crystalline aliphatic polyamide denoted E and having an average number of carbon atoms per nitrogen atom denoted CE = CD - 1, preferably CE = CD - 2; from 0 to 25% by weight of a semi-crystalline aliphatic polyamide denoted F having an average number of carbon atoms per nitrogen atom denoted CF = CE - 1, preferably CF = CE - 2; from 3 to 45% by weight of at least one impact modifier, in particular from 5 to 20% by weight of at least one impact modifier; from 0 to 20% of at least one plasticizer;from 0 to 2% by weight of at least one additive, from 0 to 35% of at least one antistatic filler, the sum of the constituents being equal to 100%.;

[0187] In another embodiment of this second variant, said layer (2) is made up of a composition made up of: at least 50% by weight, in particular from 50% to 97% by weight, by weight, in particular from 50% to 95% by weight, of at least one semi-crystalline aliphatic polyamide denoted D having an average number of carbon atoms per nitrogen atom denoted CD of from 6 to 18, advantageously from 9 to 15; from 0 to 25% by weight of at least one semi-crystalline aliphatic polyamide denoted E and having an average number of carbon atoms per nitrogen atom denoted CE = CD - 1, preferably CE = CD - 2; from 0 to 25% by weight of a semi-crystalline aliphatic polyamide denoted F having an average number of carbon atoms per nitrogen atom denoted CF = CE - 1, preferably CF = CE - 2; from 3 to 45% by weight of at least one impact modifier, in particular from 5 to 20% by weight of at least one impact modifier; from 0 to 20% of at least one plasticizer;from 0 to 2% by weight of at least one additive, from 0 to 35% of at least one antistatic filler, the sum of the constituents being equal to 100%.;

[0188] In yet another embodiment of this second variant, said layer (2) is made up of a composition comprising: at least 50% by weight, in particular from 50% to 97% by weight, in particular from 50% to 95% by weight, of at least one semi-crystalline aliphatic polyamide denoted D having an average number of carbon atoms per nitrogen atom denoted CD of from 6 to 18, advantageously from 9 to 15; from 0 to 50% by weight of at least one semi-crystalline aliphatic polyamide denoted E and having an average number of carbon atoms per nitrogen atom denoted CE = CD - 1, preferably CE = CD - 2; from 0 to 50% by weight of a semi-crystalline aliphatic polyamide denoted F having an average number of carbon atoms per nitrogen atom denoted CF = CE - 1, preferably CF = CE - 2;from 3 to 45% by weight of at least one impact modifier, in particular from 5 to 20% by weight of at least one impact modifier, from 0 to 20% by weight of at least one plasticizer, from 0 to 2% by weight of at least one additive, from 0 to 35% of at least one antistatic filler, the sum of the constituents being equal to 100%.;

[0189] Advantageously, the composition of said layer (2) comprises a PA11, a PA12 or a PA612 and from 3 to 45% by weight of an impact modifier, in particular from 5 to 20% by weight of an impact modifier. With regard to the structure

[0190] All embodiments of layer (1) described above in the paragraph "regarding layer (1)" can be used for the structure detailed in this part.

[0191] Advantageously, said layer (1) is the layer in contact with the transported fluid. Advantageously, the composition of said layer (2) comprises a PA11, a PA12 or a PA612 and the recycled material comes from a single-layer tube consisting of a composition comprising only a PA11, in particular the composition of the layer (1) consists of 100% recycled material.

[0192] Advantageously, the composition of said layer (2) comprises a PA11, a PA12 or a PA612, the recycled material comes from a single-layer tube consisting of a composition comprising only a PA11, in particular the composition of the layer (1) consists of 100% recycled material and the composition of said layer (2') comprises a PA11, a PA12 or a PA612.

[0193] Advantageously, the composition of said layer (2) comprises a PA1 1 , a PA12 or a PA612 and from 3 to 45% by weight of at least one impact modifier, in particular from 5 to 20% by weight of at least one impact modifier and the recycled material comes from a single-layer tube consisting of a composition comprising only a PA1 1 , in particular the composition of the layer (1 ) consists of 100% recycled material. In one embodiment, said layer (1 ) represents at least 10%, in particular at least 30%, in particular at least 50% of the total thickness of said multi-layer tubular structure (MLT).

[0194] Advantageously, said layer (1) represents at least 60%, in particular at least 70% of the total thickness of said multi-layer tubular structure (MLT).

[0195] In one embodiment of the multilayer tubular structure (MLT), said composition of said layer (1) is free of polyamides noted A and B and said composition of said layer (2) comprises polyamides chosen from those noted E, F and a mixture thereof.

[0196] In another embodiment of the multilayer tubular structure (MLT), said composition of said layer (1) comprises polyamides chosen from those noted A, B and a mixture thereof, and said composition of said layer (2) is free of polyamides noted E and F.

[0197] In yet another embodiment of the multilayer tubular structure (MLT), said composition of said layer (1) comprises polyamides chosen from those T1 noted A, B and a mixture thereof, and said composition of said layer (2) comprises polyamides chosen from those noted E, F and a mixture thereof.

[0198] In yet another embodiment of the multilayer tubular structure (MLT), said composition of said layer (1) is free of polyamides noted A and B and said composition of said layer (2) is free of polyamides noted E and F.

[0199] Advantageously, in these last four embodiments, the layer (1) comes from a single-layer recycled tube.

[0200] Advantageously, in these last four embodiments, the layer (1) comes from a single-layer recycled tube and only said composition of said layer (1) comprises at least one impact modifier.

[0201] Advantageously, in these last four embodiments, the layer (1) comes from a single-layer recycled tube and said composition of said layer (1) as well as said composition of the layer (2) comprises at least one impact modifier.

[0202] Advantageously, in these last four embodiments, the layer (1) comes from a recycled multi-layer tube.

[0203] Advantageously, in these last four embodiments, the layer (1) comes from a recycled multi-layer tube and only said composition of said layer (1) comprises at least one impact modifier.

[0204] Advantageously, in these last four embodiments, the layer (1) comes from a recycled multi-layer tube and said composition of said layer (1) as well as said composition of the layer (2) comprises at least one impact modifier.

[0205] In one embodiment, said multi-layer tubular (MLT) is intended for the transport of fluids chosen from a fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline or diesel, in particular bio-diesel.

[0206] EXAMPLES:

[0207] The following resins were used in the various compositions of the invention: PA1 1: Polyamide 1 1 of Mn (number molecular weight) 29000. The melting temperature is 190 °C, its enthalpy of fusion is 56 kJ / m2. The composition of this PA1 1 includes 0.25% (+ / -0.05%) of H3PO4.

[0208] PA12: Polyamide 12 of Mn (number molecular weight) 35000. The melting temperature is 178°C, its enthalpy of fusion is 54kJ / m2

[0209] PA1012: Polyamide 1012 of Mn (number molecular weight) 27000. The melting temperature is 190 °C, its enthalpy cb fusion is 57kJ / m2

[0210] The melting temperature and the enthalpy of fusion were determined according to the ISO 11357-3:2013 standard. The following additives, plasticizers and impact modifiers were used in the compositions of the invention: stabilizer: stabilizer consisting of 80% Lowinox® 44B25 phenol from Great Lakes, 20% Irgafos® 168 phosphite from Ciba BBSA: BBSA plasticizer (benzyl butyl sulfonamide),

[0211] Imod = generically designates an impact modifier of polyolefin type or other such as PEBA (polyether-block-amide), core-shell particles, silicones, etc.

[0212] Imodl: 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.

[0213] Imod2: impact modifier type ethylene / ethyl acrylate / anhydride in mass ratio 68.5 / 30 / 1.5 and MFI 6 at 190°C under 2.16 kg.

[0214] Imod3: impact modifier type ethylene / butyl acrylate / anhydride in mass ratio 79 / 18 / 3 and MFI 5 at 190°C under 2.16 kg.

[0215] The following compositions were used to manufacture the tubes according to the invention:

[0216] Throughout the description all percentages are given by weight.

[0217] In the case of the compositions called “recy”, “recy2” and “recy3” used for layer (1) of the tubes of the invention or the counter-example tubes, protocols for simulating an aged tube were used:

[0218] Protocol A: The tube is (artificially) aged according to an easily reproducible model protocol which consists of placing it in air (in the presence of oxygen) at 150 °C for 96 hours (4 days), in order to thermo-oxidize it. This model aging is representative of the average thermo-oxidation that the tubes undergo over 10 years of service in a vehicle next to a hot engine.

[0219] The results obtained on impact, aging, flexural modulus, adhesion and elongation show that protocol A is representative of a reground gasoline tube. Specific protocols used during (re)compounding of the aged tube.

[0220] After aging, the crushed tube can in certain cases be recompounded according to two protocols:

[0221] Protocol B: The reground tube is recompounded on a Coperion / Werner® 40mm twin-screw extruder, 70kgh, 300rpm, 270°C set point, with a degassing of -100mmHg. Protocol B2: The reground tube is recompounded on a Coperion / Werner® 40mm twin-screw extruder, 70kgh, 300rpm, 270°C set point, with a strong degassing of -660mmHg.

[0222] The different compositions used for the preparation of the tubes of the invention are as follows:

[0223] PA1 1 PL = PA1 1 + 7% BBSA + 1% stabilizer

[0224] PA12PL = PA12 + 12% BBSA + 1% stabilizer

[0225] PA1 1 PL-recy = PA11 PL tube aged according to protocol A, reground, to then be recycled.

[0226] PA1 1 PL-recy2 = PA1 1 PL tube aged according to protocol A, reground, recompounded according to protocol B2, with during this recompounding the addition of 7% BBSA + 0.5% stabilizer, to then be recycled

[0227] PA1 1 PL-recy + 50%PA12PL-recy = a 50 / 50 blend of PA11 PL-recy and PA12PL-recy granules.

[0228] PA1 1 PL-recy3 = PA1 1 PL tube aged according to protocol A, reground, recompounded according to protocol B2, recompounding with strong degassing, with during this recompounding addition of 6% imod3 and 5% BBSA and 0.5% stabilizer.

[0229] PA12PL-recy = PA12PL tube aged according to protocol A, reground, to then be recycled.

[0230] PA12imod1 = PA12 + 6% imodl + 8%BBSA +1% stabilizer

[0231] PA1012PL4 = PA1012 + 12% BBSA + 1% stabilizer

[0232] 1012-recy = PA1012PL4 tube aged according to protocol A, reground, to be then recycled

[0233] PA12HIP-recy3 = PA12HIPHL tube aged according to protocol A, reground, recompounded according to protocol B, with during this recompounding addition of 6%imod1, 9%BBSA and 1% stabilizer; then intended to be recycled

[0234] PA1 1 NX3 = PA1 1 + imod2 10% + PA610 5% + PA6 5% + BBSA 4% + stabilizer 1%

[0235] PA1 1 NX3-recy2 = PA1 1 NX3 tube aged according to protocol A, reground, recompounded according to protocol B2, recompounding with strong degassing, with the addition of 3% BBSA and 0.5% stabilizer during this recompounding.

[0236] PA1 1 PL-recyNX3 = PA1 1 PL tube aged according to protocol A, reground, recompounded according to protocol B, with during this recompounding addition of imod2 10% + PA610 5% + PA6 5% + BBSA 4% + stabilizer 1%, to be then recycled PA12HIPHL= PA12 + 6% imodl + 10%BBSA + 1% stabilizer PA12HIPHL-recy2 = PA12HIPHL tube aged according to protocol A, reground, recompounded according to protocol B, with during this recompounding addition of 10% BBSA + 0.5% stabilizer, to be then recycled

[0237] PA12HIP-recy3 = PA12HIPHL tube aged according to protocol A, reground, recompounded according to protocol B, with during this recompounding addition of 6%imod1, 9% BBSA and 1% stabilizer; then intended to be recycled

[0238] These compositions are manufactured by conventional compounding in a co-rotating twin-screw extruder of the Coperion® 40 type, at 300 rpm, at 270 °C (or at 300 °C when the ingredients have a melting point above 260 °C).

[0239] Multilayer tubes of the invention:

[0240] The layers are described from the outside to the inside, followed by their respective thicknesses indicated in the form of %; the tubes are of dimension 8*1 mm Preparation of the multilayer structures (tubes):

[0241] Multilayer tubes are produced by coextrusion. A Maillefer® industrial multilayer extrusion line is used, equipped with 5 extruders, connected to a multilayer extrusion head with spiral mandrels.

[0242] 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 co-extrusion head; the inner diameter of the die and the outer 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. Water circulates in this tank, generally maintained at 20 °C, into which a gauge is immersed to conform the tube to its final dimensions.The diameter of the gauge is adapted to the dimensions of the tube to be produced, typically from 8.5 to 10 mm for a tube with an external diameter of 8 mm and a thickness of 1 mm; a succession of cooling tanks in which water is maintained at around 20°C, allowing the tube to be cooled along the path from the head to the drawing bench; a diameter gauge; a drawing bench.

[0243] The 5-extruder configuration is used to produce tubes ranging from 2 layers to 5 layers (and also single-layer tubes). 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 drying step is carried out before testing, generally in a vacuum dryer, for 1 night at 80°C.

[0244] The tubes, which meet the characteristics described in this patent application, were taken after stabilization of the extrusion parameters, the dimensions of the tubes targeted no longer changing over time. The diameter is controlled by a laser diameter meter installed at the end of the line.

[0245] Line speed is typically 20m / min. It generally varies between 5 and 100m / min.

[0246] The screw speed of extruders depends on the layer thickness and screw diameter as is known to those skilled in the art.

[0247] 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.

[0248] The multilayer tubes produced by extrusion above were then evaluated on several criteria:

[0249] Flexural modulus (Flex.): refers to the flexural modulus measured according to ISO178 at 23°C on a tube conditioned at equilibrium in a 50% humidity climate and at 23°C

[0250] We note "+", a flexibility that can be described as "good", which corresponds to <= 1000 MPa and > 500 MPa

[0251] We note "++", a flexibility that can be described as "very good", which corresponds to <= 500 MPa and > 250 MPa

[0252] Shock: refers to the VW-40°C type shock, VW standard TL52435 2010

[0253] We note "++", a shock performance that we can qualify as "very good", which corresponds to <= 10% breakage.

[0254] We note "+", a shock performance that we can qualify as "good", which corresponds to <= 25% breakage and > 10% breakage

[0255] We note a shock performance that can be described as "quite bad", which corresponds to <= 75% breakage and > 25%

[0256] We note a shock performance that can be described as "very poor", which corresponds to > 75% Aging (Age.): this is the durability, in other words it designates the resistance of the tube to oxidative aging in hot air. The tube is aged in air at 150 °C, then it is shocked with a shock according to the DIN 73378 standard, this shock being carried out at -40 °C, the half-life (in hours) is indicated which corresponds to the time after which 50% of the tubes tested break. A qualitative comment accompanies this value.

[0257] We note "++", a durability that can be described as "very good", which corresponds to >= 200h of half-life.

[0258] We note "+", a durability (resistance to thermo-oxidative aging) that we can qualify as "good", which corresponds to >= 10Oh of half-life (and <200h)

[0259] We note a durability (resistance to thermo-oxidative aging) that can be described as "acceptable", which corresponds to >= 50h of half-life (and <1 OOh)

[0260] We note a durability (resistance to thermo-oxidative aging) that can be described as "poor", which corresponds to <50h

[0261] In the case where a half-life figure is given to show nuances, this figure is rounded up by 25h increments, to take into account significant figures, linked to the precision of the evaluation.

[0262] Adhesion (Adh.): this is the adhesion force. It is translated by the measurement of the peel force, expressed in N / cm, and measured on the tube of diameter 8 mm and thickness 1 mm having undergone conditioning of >=15 days at 50% relative humidity at 23°C, such that hygroscopic equilibrium is reached within the sample.

[0263] The value given concerns the weakest interface, i.e. the least adherent of the multilayer, where there is therefore the greatest risk of detachment. Peeling is carried out at the interface by subjecting one of the parts to traction at an angle of 90° and at a speed of 50mm / min according to the following process.

[0264] A 9mm wide strip of tube is cut. This strip is therefore tile-shaped and still contains all the layers of the original tube. The separation of the two layers of the interface, which we wish to evaluate, is started using a knife. Each of the layers thus separated is placed in the jaws of a tensile machine. The peeling is carried out by pulling these two layers on either side at 180 degrees and at a speed of 50 mm / min. The strip, and therefore the interface, is kept at 90 degrees relative to the direction of traction.

[0265] We note:

[0266] +++: very good, > 50

[0267] ++: good, >20 and <=50

[0268] +: quite good (acceptable), >10 and <=20 -: bad, <= 10

[0269] Elongation at break (All.%): this is the elongation at break carried out according to ISO R527 standard except that measured on a tube with a diameter of 8mm and a thickness of 1mm. The sample is ISO conditioned, this is a conditioning of >=15 days at 50% relative humidity at 23°C such that hygioscopic equilibrium is reached within the sample.

[0270] We note:

[0271] +++: very good, >=200% elongation

[0272] ++: good, >=100 and <200% elongation +: unsatisfactory: <100% elongation

[0273] The results are shown in Table 1.

[0274] [Tables 1]

Claims

DEMANDS 1. Multilayer tubular structure (MLT) intended for the transport of automotive fluids, in particular air, oil, water, urea solution, glycol-based coolant, or fuel such as gasoline, in particular alcoholic gasoline, bio-gasoline, or diesel, in particular biodiesel, or hydrogen, consisting of two layers: a layer (1) consisting of a composition comprising predominantly at least one semi-crystalline aliphatic polyamide, said composition being made of at least 50% recycled material from a single-layer and / or multilayer tube having been intended for the transport of automotive fluids, in particular as defined above, said tube being made of a composition comprising predominantly at least one polyamide, said tube having undergone various treatments selected from grinding and then recompounding, i.e. that after grinding,The crushed particles are fed into an extruder, in particular a co-rotating twin-screw type, or a co-mixer type (Buss), where they are remixed by melting, and a grinding then a recompounding and then a reformulation, that is to say that after grinding, the crushed particles are fed into an extruder, in particular a co-rotating twin-screw type, or a co-mixer type (Buss), where they are remixed by melting with the addition of at least one compound chosen from a semi-crystalline aliphatic polyamide, of recycled or non-recycled origin, at least one impact modifier, a plasticizer, an additive and antistatic fillers in order to be recyclable, a simple single grinding being excluded from the different treatments, a layer (2) consisting of a composition comprising predominantly at least one semi-crystalline aliphatic polyamide and optionally at least one impact modifier,and when layer (2) is made of a composition comprising predominantly at least one semi-crystalline aliphatic polyamide which is PA12 and / or PA612 and / or PA1010, then said composition includes said impact modifier, and said layer (2) being made of at least 90% non-recycled material.

2. Multilayer tubular structure (MLT) according to claim 1, wherein layer (1) is the layer in contact with the fluid.

3. Multilayer tubular structure (MLT) according to claim 1 or 2, wherein said layer (1) represents at least 10%, in particular at least 30%, in particular at least 50% of the total thickness of said multilayer tubular structure (MLT).

4. Multilayer tubular structure (MLT) according to any one of claims 1 to 3, wherein said layer (1) is made up of a composition comprising: at least 50% by weight, in particular from 50% to 97% by weight, of at least one semi-crystalline aliphatic polyamide denoted C having an average number of carbon atoms per nitrogen atom denoted Ce of 6 to 18, advantageously from 8 to 12; from 0 to 25% by weight of at least one semi-crystalline aliphatic polyamide denoted B and having an average number of carbon atoms per nitrogen atom denoted CB = Ce - 1, preferably CB = Ce - 2; from 0 to 25% by weight of a semi-crystalline aliphatic polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA = CB - 1, preferably CA = CB - 2;from 0 to 45% by weight of at least one shock modifier, in particular from 3 to 45% by weight of at least one shock modifier, from 0 to 20% by weight of at least one plasticizer, from 0 to 2% by weight of at least one additive, the sum of the constituents being equal to 100%.

5. Multilayer tubular structure (MLT) according to any one of claims 1 to 4, wherein the recycled material is from a single-layer and / or multilayer tube selected from a single-layer and / or multilayer tube that is ground and recompounded, and a single-layer and / or multilayer tube that is ground, recompounded and reformulated.

6. Multilayer tubular structure (MLT) according to claim 5, wherein said layer composition (1) is free of plasticizer and / or shock modifier and said recycled material is derived from a single-layer and / or multilayer tube selected from a ground and recompounded single-layer and / or multilayer tube, and a ground, recompounded and reformulated single-layer and / or multilayer tube.

7. Multilayer tubular structure (MLT) according to claim 5, wherein said layer composition (1) comprises at least one compound selected from plasticizer, shock modifier and additive, and said recycled material is derived from a single-layer and / or multilayer tube that is ground up and then recompounded and reformulated.

8. Multilayer tubular structure (MLT) according to any one of claims 1 to 7, wherein the fluid transported by said single-layer and / or multilayer tube is the same as that of said multilayer tubular structure (MLT).

9. Multilayer tubular structure (MLT) according to any one of claims 1 to 7, wherein the fluid transported by said single-layer and / or multilayer tube is different from that of said multilayer tubular structure.

10. Multilayer tubular structure (MLT) according to any one of claims 1 to 9, wherein the layer (2) is made up of a composition comprising: at least 50% by weight, in particular from 50% to 97% by weight, in particular from 50% to 95% by weight, of at least one semi-crystalline aliphatic polyamide denoted D having an average number of carbon atoms per nitrogen atom denoted CD of 6 to 18, advantageously from 9 to 15; from 0 to 50% by weight of at least one semi-crystalline aliphatic polyamide denoted E and having an average number of carbon atoms per nitrogen atom denoted CE = CD - 1, preferably CE = CD - 2; from 0 to 50% by weight of a semi-crystalline aliphatic polyamide denoted F having an average number of carbon atoms per nitrogen atom denoted CF = CE - 1 , preferably CF = CE - 2;from 3 to 45% by weight of at least one shock modifier, in particular from 5 to 20% by weight of at least one shock modifier, from 0 to 20% by weight of at least one plasticizer, from 0 to 2% by weight of at least one additive, from 0 to 35% of at least one antistatic filler, the sum of the constituents being equal to 100%.; 11. Multilayer tubular structure (MLT) according to any one of claims 10, wherein said composition of said layer (1) is devoid of polyamides denoted A and B and said composition of said layer (2) comprises polyamides selected from those denoted E, F and a mixture thereof.

12. Multilayer tubular structure (MLT) according to any one of claims 10, wherein said composition of said layer (1) comprises polyamides selected from those denoted A, B and a mixture thereof, and said composition of said layer (2) is devoid of polyamides denoted E and F.

13. Multilayer tubular structure (MLT) according to any one of claims 10 to 12, wherein layer (1) is derived from a recycled single-layer tube.

14. Multilayer tubular structure (MLT) according to any one of claims 10 to 12, wherein said tube is a multilayer tube 15. Multilayer tubular structure (MLT) according to any one of claims 1 to 14, wherein the Tf of the major aliphatic semi-crystalline polyamide of layer (1) is <225°C, in particular <200°C as determined by DSC according to standard 60 11357- 3:2013, at a heating speed of 20K / min.

16. Multilayer tubular structure (MLT) according to any one of claims 1 to 15, wherein the major aliphatic semi-crystalline polyamide of layer (1) has an enthalpy of crystallization > 25 J / g, preferably > 40 J / g, in particular > 45 J / g as determined by DSC according to ISO 1 1357-3:2013, at a heating rate of 20K / min.

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