INJECTION MOLDING COMPOSITIONS COMPRISING RECYCLED POLYAMIDES FROM THE EXPLOITATION OF OIL OR GAS DEPOSITS, UNDER THE SEA OR ON LAND.

Abstract

The present invention relates to a molding composition comprising by weight: a) from 35 to 100%, in particular from 35 to 91.9%, of at least one semi-crystalline aliphatic polyamide PA1 comprising at least 30%, in particular at least 50%, of recycled semi-crystalline aliphatic polyamide PA2 from used or end-of-life pipelines from subsea or onshore oil or gas fields, in particular subsea, said recycled semi-crystalline aliphatic polyamide PA2 having undergone a washing and / or compounding step after removal and grinding into granules of said pipeline; b) from 0 to 65%, in particular from 5 to 50%, of at least one reinforcing fiber; c) from 0 to 40%, in particular from 3 to 30%, of at least one shock modifier; d) from 0 to 30%, in particular 0 to 15% of a charge, e) from 0 to 10%, in particular from 0.1 to 5% of at least one additive, the sum of the components a + b + c + d + e is equal to 100%.

Description

Description Title of the invention: MOLDING COMPOSITIONS FOR INJECTION COMPRISING RECYCLED POLYAMIDES FROM THE EXPLOITATION OF OIL DEPOSITS OR OF GAS, UNDER SEA OR ON LAND.

[0001] — The present invention relates to molding compositions for injection including recycled polyamides from the exploitation of oil deposits or of gas, under the sea or on land. Prior art

[0002] — In the exploitation of oil or gas deposits under the sea (off-shore) or onshore it is necessary to use flexible pipes to connect the various devices around the platform. These pipes must be resistant to oil hot, gas, water and mixtures of at least two of these products for durations of up to 20 years. These pipes are generally made of a layer non-waterproof metal interior formed by a profiled metal strip rolled into helix such as a stapled strip that gives the shape to the pipe, then on this layer a polymer is extruded to provide waterproofing and finally other layers are added protection and reinforcement such as metallic fiber sheets and rubbers.

[0003] — Long-chain polyamides have been used for years for the exploitation of oil or gas deposit, underwater or on land.

[0004] — However, it is necessary to clean these hoses by circulating methanol through them. for example to remove hydrates. The disadvantage of methanol is that it penetrates strongly in the polyamide. There are therefore losses of methanol but also it can extract the plasticizer and / or modifiers from the polyamide which leads to a de- gradation of mechanical properties and premature aging of the hose.

[0005] — In addition, several tens to hundreds of tons of long-chain polyamides from of oil or gas field exploitation pipes, underwater or on land (respectively offshore or onshore pipes) will have to be recycled in the next few years due to the fact that they have reached the end of their life. However, these polyamides do not cannot be used after simple grinding because of pollutants from the oil or gas extracted from them,

[0006] — Polyamides (PA) from oil field exploitation pipes or gas, underwater or on land cannot be used as is.

[0007] — They must be crushed in order to be able to be transformed into a part having a different shape for different application.

[0008] = After broving, the polyamide to be recycled must also be washed and / or compounded in order to extract a large majority of pollutants (with solvents, melted, under vacuum, etc.). However, the extraction is not necessarily complete. Without this washing and / or compounding step, the manufactured parts will exude. This exudate can be toxic to the user, for example during the processing stage, and can create a greasy appearance on the finished parts. Furthermore, the polyamides to be recycled may be largely hydrolyzed and therefore cannot be extruded. In this case, they must therefore be exposed to a high vacuum (with the possible addition of catalyst) to increase their viscosity and make them injectable. It is therefore necessary to have a composition that does not release harmful gases during the implementation stage and does not exude over time. This allows on the one hand to be injected safely by the manipulator and on the other hand to obtain all types of injected part stable over time. The present invention therefore relates to a molding composition comprising by weight: a) from 35 to 100%, in particular from 35 to 91.9% of at least one semi-crystalline aliphatic polyamide PA1 comprising at least 30%, in particular at least 50% of recycled semi-crystalline aliphatic polyamide PA2 from used or end-of-life pipes for the exploitation of oil or gas deposits under the sea or on land, in particular under the sea, said recycled semi-crystalline aliphatic polyamide PA2 having undergone a washing and / or compounding step after removal and grinding in the form of granules from said pipe; (b) from 0 to 65%, in particular 5 to 50% of at least one reinforcing fibre; (c) from 0 to 40%, in particular from 3 to 30% of at least one impact modifier; d) from 0 to 30%, in particular from 0 to 15% of a load, (e) from 0 to 15%, in particular from 0.1 to 10%, in particular from 0.5 to 5% of at least one additive, the sum of the components a + b + € + d + e is equal to 100%. The inventors have therefore found that the addition of a recycled polyamide PA2 from pipes used or at the end of their life from the exploitation of oil or gas fields under the sea or on land, in particular under the sea, to a virgin polyamide PA1 makes it possible to obtain an injectable composition, having good mechanical properties, exuding little and making it possible to improve the quality and productivity of the welds between two parts. injectable. Said composition is implemented in complete safety for the handler because it does not emit harmful or toxic gases and makes it possible to obtain all types of injected parts which do not exude or which have low exudation. The exploitation of oil or gas deposits under the sea or onshore gas uses flexible pipes to connect the different underwater or onshore devices respectively from the platform and transporting the extracted hydrocarbons. These pipes must withstand hot oil, gas, water and mixtures of at least two of these products for periods of up to 20 years. The term "used" means that the pipe has already been used for the exploitation of oil or gas fields, whether underwater or onshore, but has not yet reached its operating limit of up to 20 years. The cessation of production on a platform and its dismantling explains the need to recycle this type of pipe which is not yet at the end of its life. The term "end of life" means that the pipe has been used for the exploitation of oil or gas fields, whether underwater or onshore, but has reached its operating limit of up to 20 years. These pipes must therefore be removed from the operating system before they are completely degraded or present a sealing problem with respect to the oil or gas transported. Regarding the semi-crystalline aliphatic polyamide PA1 Polyamide PA1 may be a homopolyamide or a copolyamide or a mixture thereof. Semi-crystalline aliphatic polyamide is understood to mean a material which is generally solid at room temperature and which softens when the temperature increases, in particular after passing its glass transition temperature (Tg), and which can exhibit a clear melting when passing its so-called melting temperature (Tf), and which becomes solid again when the temperature decreases below its crystallization temperature. Tg, Tc and Tf are determined by differential scanning calorimetry (DSC) according to 11357-2:2013 and 11357-3:2013 respectively. The number-average molecular mass Mn of said semi-crystalline polyamide is preferably in a range from 10,000 to 85,000, in particular from 10,000 to 60,000, preferably from 10,000 to 50,000, even more preferably from 12,000 to 50,000. The nomenclature used to define polyamides is described in ISO 1874-1:2011 "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. Said at least one aliphatic semi-crystalline polyamide PAI can be 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 X with at least one dicarboxylic acid Y or from their mixtures. When said at least one aliphatic semi-crystalline polyamide PAI is obtained from the polycondensation of at least one lactam, said at least one lactam may be chosen from a C6 to C18, C8 to C18, preferably C10 to C18, more preferably C10 to C12 lactam. A C6 to C18 lactam is in particular caprolactam, decanolactam, undecanolactam, and lauryllactam. When said at least one aliphatic semi-crystalline polyamide PAI is obtained from the polycondensation of at least one lactam, it can therefore comprise a single lactam or several lactams. Advantageously, said at least one aliphatic semi-crystalline polyamide PAI is obtained from the polycondensation of a single lactam and said lactam is chosen from lauryllactam and undecanolactam, advantageously lauryllactam. When said at least one aliphatic semi-crystalline polyamide PAI is obtained from the polycondensation of at least one amino acid, said at least one amino acid may be chosen from a C8 to C18 amino acid, preferably a C10 to C18 amino acid, more preferably a C10 to C12 amino acid. A C8 to C18 amino acid includes 9-aminononanoic acid, 10-aminodecanoic acid, 10-aminoundecanoic acid, 12-aminododecanoic acid, and 11-aminoundecanoic acid, as well as its derivatives, including N-heptyl-11-aminoundecanoic acid. When said at least one aliphatic semi-crystalline polyamide PAI is obtained from the polycondensation of at least one amino acid, it can therefore comprise a single amino acid or several amino acids. Advantageously, said aliphatic semi-crystalline polyamide PAI is obtained from the polycondensation of a single amino acid and said amino acid is chosen from 10-aminodecanoic acid, 11-aminoundecanoic acid and 12-aminododecanoic acid, advantageously 1-aminoundecanoic acid. When said at least one aliphatic semi-crystalline polyamide PAI is obtained from the polycondensation of at least one diamine X with at least one aliphatic dicarboxylic acid Y, the diamine X is C4-C36, preferably C6-C18, preferably C6-C12, more preferably C10-C12 and said aliphatic dicarboxylic acid Y is C6-C36, preferably C6-C18, preferably C6-C12, more preferably C10-C12 The diamine can be linear or branched. Advantageously, it is linear. Said at least one C4-C36 diamine X may in particular be chosen from 1-4 butanediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethyldiamine, 1,13-tridecamethylenediamine, 1,14-tetradecamethylenediamine, 1,16-hexadecamethylenediamine and 1,18-octadecamethylenediamine, octadecenediamine, eicosanediamine, docosanediamine and diamines obtained from fatty acids. Advantageously, said at least one diamine X is C4-C18 and chosen from 1-4 butanediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine, 1,13-tridecamethylenediamine, 1,14-tetradecamethylenediamine, 1,16-hexadecamethylenediamine and 1,18-octadecamethylenediamine. Advantageously, said at least one diamine X in C6 to C12, is in particular chosen from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, la 1,12-dodecamethylenediamine. Advantageously, said at least one diamine X in C6 to C12, is in particular chosen from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, la 1,12-dodecamethylenediamine. Advantageously, the diamine X used is C10 to C12, in particular chosen from 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine. Said at least one C6 to C36 dicarboxylic acid Ÿ may be chosen from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, and diacids obtained from fatty acids. The diacid can be linear or branched. Advantageously, it is linear. Advantageously, said at least one dicarboxylic acid Y is C6 to C18 and is chosen from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid. Advantageously, said at least one dicarboxylic acid Ÿ is C6 to C12 and is chosen from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid. Advantageously, said at least one dicarboxylic acid Ÿ is C10 to C12 and is chosen from sebacic acid, undecanedioic acid, dodecanedioic acid. When said aliphatic semi-crystalline polyamide PA1 is obtained from the polycondensation of at least one diamine X with at least one dicarboxylic acid Y, it can therefore comprise a single diamine or several diamines and a single dicarboxylic acid or several dicarboxylic acids. Advantageously, said aliphatic semi-crystalline polyamide PAI is obtained from the polycondensation of a single diamine X with a single dicarboxylic acid Y. In one embodiment, the recycled semi-crystalline aliphatic polyamide PAI is a long-chain polyamide having an average number of carbon atoms per nitrogen atom greater than 7, in particular greater than 9. Regarding recycled semi-crystalline aliphatic polyamide PA2 Polyamide PA2 may be a homopolyamide or a copolyamide or a mixture thereof. Semi-crystalline aliphatic polyamide is understood to mean a material which is generally solid at room temperature and which softens when the temperature increases, in particular after passing its glass transition temperature (Tg), and which can exhibit a clear melting when passing its so-called melting temperature (Tf), and which becomes solid again when the temperature decreases below its crystallization temperature. Tg, Tc and Tf are determined by differential scanning calorimetry (DSC) according to 11357-2:2013 and 11357-3:2013 respectively. The number-average molecular mass Mn of said semi-crystalline polyamide is preferably in a range from 10,000 to 85,000, in particular from 10,000 to 60,000, preferably from 10,000 to 50,000, even more preferably from 12,000 to 50,000. Said at least one aliphatic semi-crystalline polyamide PA2 was initially obtained before use for the exploitation of oil or gas deposits 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 X with at least one dicarboxylic acid Y or from their mixtures as described above for the semi-crystalline aliphatic polyamide PAI. Advantageously the PA 2 is a PA 11 or PA 12, in particular the PA1I1. After use, i.e. when it is worn out or at the end of its life, the pipe for exploiting oil or gas deposits under the sea or on land, in particular under the sea, is removed from the exploitation platform, the different layers are separated and the layers containing the PA 2 are ground in the form of ground material (0.5 mm to 25 mm) or powder (to a size less than 0.5 mm) then washed and / or compounded, i.e. the ground material, after washing or not, is introduced at least once into an extruder, in particular of the co-rotating twin-screw type, or of the co- mixer (Buss), where the ground material is remixed by melting, with or without the addition of at least one catalyst. The molten material comes out of the extruder in rods which are cooled and cut into granules. Advantageously, the number of compoundings is from 1 to 10, in particular from 1 to 5, in particular the number of compoundings is 1, 2, 3, 4 or 5, in particular 1, 2 or 3. Washing of the ground material when it takes place can be carried out in particular using a solvent, in particular methanol, ethanol, in order to extract a large majority of pollutants, as described below and coming from the operation. Compounding when it takes place can be carried out with the addition of a catalyst. The term "catalyst" refers to a polycondensation catalyst such as a mineral or organic acid. Advantageously, the proportion by weight of catalyst is from approximately 50 ppm to approximately 5000 ppm, in particular from approximately 100 to approximately 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. Advantageously, the present invention therefore relates to the use defined above of at least one catalyst, in a proportion by weight of catalyst of from approximately 50 ppm to approximately 5000 ppm, in particular from approximately 100 to approximately 3000 ppm relative to the total weight of the composition, of at least one organic or copper thermal stabilizer and of at least one chain extender chosen from polycarbodiimide, polymaleic anhydride and polyepoxy, with a matrix comprising at least one thermoplastic polymer, in particular a polyamide, said catalyst being chosen from phosphoric acid (H3PO4), phosphorous acid (H3PO3), hypophosphorous acid (H3PO2), or a mixture thereof. Advantageously, the catalyst is chosen from phosphoric acid (H3PO4), phosphorous acid (H3PO3) in a proportion of approximately 100 to approximately 3000 ppm. In one embodiment, the PA2 mixture to be recycled is degassed during compounding. In one embodiment, the outgassing is low, meaning that the outgassing is from -50 mmHg to -150 mmHg. For example, it is carried out according to the following protocol: The crushed tube, washed or not, is compounded on a Coperion / Werner 40mm twin-screw extruder, 70kgh, 300rpm, 270°C setpoint, with a degassing of -100mmHeg. In another embodiment, the outgassing is strong, meaning that the degassing is included from -550 mmHeg to -750 mmHeg. For example, it is performed according to the following protocol B: The crushed tube, washed or not, is compounded on a Coperion / Werner 40mm twin-screw extruder, 70kg / h, 300rpm, 270°C setpoint, with strong degassing of -660mmHg. Advantageously, the degassing is located just after the melting zone in the extruder. Advantageously, the inherent viscosity of the semi-crystalline aliphatic polyamide after grinding and washing or after grinding and compounding with or without catalyst, or after grinding, washing and compounding with or without catalyst, as determined according to ISO 307:2007 in m-cresol at 20°C is less than 1.6 dl / g dl / g, in particular from 0.9 dl / g to 1.5 dl / g. The ground, washed and / or compounded semi-crystalline aliphatic polyamide, with or without catalyst, with or without degassing, therefore corresponds to the recycled semi-crystalline aliphatic polyamide PA2 of the composition of the invention. In one embodiment, the recycled semi-crystalline aliphatic polyamide PA2 is a long-chain polyamide having an average number of carbon atoms per nitrogen atom greater than 7, in particular greater than 9. In particular, recycled semi-crystalline aliphatic polyamide PA2 is a long-chain polyamide having an average number of carbon atoms per nitrogen atom of more than 7 to 12, in particular more than 7 to 11, in particular more than 9 to 12, in particular more than 9 to 11. In another embodiment, said recycled semi-crystalline aliphatic polyamide PA2 comprises at least one species chosen from alkanes, C14 to C18 aliphatic mono acids, mono or polyaromatic compounds and aromatic acids. Alkanes include methylcyclopentane, cyclohexane, methylcyclohexane, 1,2-cis-dimethylcyclohexane, 1,2-trans-dimethylcyclohexane, 1,3-cis-dimethylcyclohexane, 1,3-trans-dimethylcyclohexane, 1,4-cis-dimethylcyclohexane, 1,4-trans-dimethylcyclohexane, or ethylcyclohexane. Aliphatic monobasic acids from C14 to C18 include palmitic acid and stearic acid. The said C14 to C18 aliphatic mono acids are also present in the initial virgin semi-crystalline aliphatic polyamide (from 1 to 100 ppm) but are present in higher concentration in the recycled semi-crystalline aliphatic polyamide PA2 (more than 100 ppm), in particular from 500 to 5000 ppm. Mono- or poly-aromatic compounds include toluene, xylene, trimethylbenzene, diphenyl methyl and diphenyl methanol, naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, 1,2-dimethylnaphthalene, 1,3-dimethylnaphthalene, 1,4-dimethylnaphthalene, 1,3,6-trimethylnaphthalene, 2,3,5-trimethylnaphthalene, 1-phenanthrene, 2-methyl phenanthrene. Aromatic acids include benzoic acid, 2-methylbenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, 2,5-dimethylbenzoic acid, 3,4-dimethylbenzoic acid, 2,4-dimethylbenzoic acid and 3,5-dimethylbenzoic acid. Advantageously, said recycled semi-crystalline aliphatic polyamide PA2 comprises at least one species chosen from sulfur compounds, alkanes, C14 to C18 aliphatic mono acids, mono or polyaromatic compounds and aromatic acids. More advantageously, said recycled semi-crystalline aliphatic polyamide PA2 comprises at least one species chosen from alkanes, mono- or poly-aromatic compounds and aromatic acids. Even more advantageously, said recycled semi-crystalline aliphatic polyamide PA2 comprises at least one species chosen from alkanes and mono or poly-aromatic compounds. Advantageously, said recycled semi-crystalline aliphatic polyamide PA2 comprises at least one species chosen from alkanes such as methylcyclopentane, cyclohexane, methylcyclohexane, 1,2-cis-dimethylcyclohexane, 1,2-trans-dimethylcyclohexane, 1,3-cis-dimethylcyclohexane, 1,3-trans-dimethylcyclohexane, 1,4-cis-dimethylcyclohexane, 1,4-trans-dimethylcyclohexane, or ethylcyclohexane and mono or polyaromatic compounds such as toluene, xylene, trimethylbenzene, diphenyl methyl and diphenyl methanol, naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, 1,2-dimethylnaphthalene, 1,3-dimethylnaphthalene, 1,4-dimethylnaphthalene, 1,3,6-trimethylnaphthalene, 2,3,5-trimethylnaphthalene, 1-phenanthrene, 2-methyl phenanthrene. In one embodiment, the mass content of said species present in the recycled semi-crystalline aliphatic polyamide PA2 is from 100 ppm to 2000 ppm, in particular from 100 ppm to 1000 ppm. In another embodiment, the recycled semi-crystalline aliphatic polyamide PA2 has a characteristic odor comprising sulfur / pyrogenic poles and / or hydrocarbons and / or aromatic, terpenic and phenolic. The above odors are determined according to the description of the field of odors® by Jean-Noël Jaubert. The field of odors, developed in 1983, provides, among other things, a methodology that allows us to describe olfactory perceptions in a common way, that is to say in excluding, as much as possible, individual evocations, It was created by a researcher Jean-Noël Jaubert from the results of a research program on the relationship between chemical structure and odorous activity of molecules present in the odorous world. Initially developed in the perfume sector, this method made it possible to describe, analyze, compare and control complete products or odorous preparations beyond the usual classifications. Discomfort related to odor issues is a signature of recycled polyamide. This discomfort is felt when opening the containers of washed or unwashed shredded material, or during extrusion and possibly on the finished product. Recycled polyamides have sulfur or aromatic odor poles (odor of aromatic solvent, naphthalene). One can distinctly smell a difference between a virgin polyamide and a recycled polyamide In yet another embodiment, the recycled semi-crystalline aliphatic polyamide PA2 has functions resulting from thermolysis reactions in an acid medium, in particular amide functions and / or methylene in alpha of said amide functions and acid chain ends, chosen from nitrile functions, ketones, and ester functions resulting from reaction of the acid functions of the polyamide with alcohols used during the life of said pipes, in a molar ratio relative to the amide functions higher than that of the same polyamide constituting an unused pipe. In one embodiment, the molar ratio of the functions resulting from thermolysis reactions is between 1 / 10000 and 1 / 20 as determined by proton NMR or by mass spectrometry after extraction or hydrolysis in an acid medium then analysis by GC / MS in electron impact. Concentrations can be measured by proton NMR in dichloromethane-d2, adding HFIP (hexafluoroisopropanol) to solubilize the polyamide. During oil extraction, alcohols are used (in the service tube) such as ethanol which can react with the acid functions of the semi-crystalline aliphatic polyamide initially present to lead to ester functions. In one embodiment, said recycled semi-crystalline aliphatic polyamide PA2 comprises a level of cyclic oligomers, chosen from oligomers having a molar mass of less than 1000 g / mol, lower than that of the equivalent virgin polyamide. The rate of cyclic oligomers is measured according to the following protocol: The recycled semi-crystalline aliphatic polyamide PA2 granules are dissolved in a HFIP (CAS RN 920-66-1) / CH2CI2 (CAS RN 75-09-3) mixture and then a non-solvent (methanol CAS RN 67-56-1) is added. The low molar masses are thus solubilized and the high molar masses precipitate. This solution is filtered at 200 μm before injection. The oligomers are evaluated as lactam equivalents 12 by reversed-phase liquid chromatography coupled with a mass spectrometer using positive electrospray ionization. Formic acid is added to enhance ionization. A peak distribution is observed due to different molar masses (from monomer to pentamer with linear or cyclic forms). Polyamide, due to fluid transport on the one hand and when washed on the other hand, has fewer oligomers than the same virgin semi-crystalline aliphatic polyamide because said transport and washing extract the cyclic oligomers. Advantageously, said recycled semi-crystalline aliphatic polyamide PA2 comprises a level of cyclic oligomers, chosen from oligomers having a molar mass of less than 1000 g / mol, of less than 90% by weight, in particular less than 50% by weight, in particular less than 20% by weight, in particular less than 10% by weight, relative to that of the equivalent virgin polyamide. Advantageously, said recycled semi-crystalline aliphatic polyamide PA2 comprises a linear oligomer content higher than that of a virgin PA. The rate of cyclic oligomer by weight in a virgin polyamide is between 500 and 10,000 ppm for each cyclic species ranging from monomer to pentamer (preferably having a mass less than 1000 gmol-1), the cyclic dimer being in particular the majority species. In particular, the rate of cyclic oligomer with a mass of less than 1000 gmol-1 is at most 4% by weight in the virgin polyamide. In one embodiment, said recycled semi-crystalline aliphatic polyamide PA2 comprises a level of cyclic oligomers having a molar mass of less than 1000 g / mol, ranging from 50 to 5000 ppm for each cyclic species ranging from monomer to pentamer, but in any case, it is lower than that of the equivalent virgin polyamide. The linear oligomer rate by weight in a virgin polyamide is between 200 and 2,000 ppm for each linear species ranging from monomer to pentamer (preferably having a mass less than 1,000 gmol-1). In one embodiment, said recycled semi-crystalline aliphatic polyamide PA2 comprises a level of linear oligomers having a molar mass of less than 1000 g / mol, ranging from 250 to 5000 ppm for each cyclic species ranging from monomer to pentamer, but in any case, it is higher than that of the equivalent virgin polyamide. In one embodiment, said recycled semi-crystalline aliphatic polyamide PA2 comprises a level of alkyl chain ends by weight, comprised from 1 ppm to 5000 ppm, advantageously 10 to 2500 ppm, said alkyl being C1 to C18 and said level being higher than that of a virgin semi-crystalline aliphatic polyamide. Regarding the composition In a first variant, the molding composition according to the invention comprises by weight: a) from 35 to 100%, in particular from 35 to 91.9% of at least one semi-crystalline aliphatic polyamide PA1 comprising at least 30%, in particular at least 50% of recycled semi-crystalline aliphatic polyamide PA2 from used or end-of-life pipes for the exploitation of oil or gas deposits under the sea or on land, in particular under the sea, said recycled semi-crystalline aliphatic polyamide PA2 having undergone a washing and / or compounding step after removal and grinding in the form of granules from said pipe; (b) from 0 to 65%, in particular from 5 to 50% of at least one reinforcing fibre; (c) from 0 to 40%, in particular from 3 to 30% of at least one impact modifier; d) from 0 to 30%, in particular 0 to 15% of a load, (e) from 0 to 10%, in particular from 0.1 to 5% of at least one additive, the sum of the components a + b + € + d + e is equal to 100%. Said composition is an injection molding composition and is not an extrusion composition. In a first embodiment of this first variant, said molding composition according to the invention comprises by weight: a) from 35 to 95%, in particular from 35 to 91.9% of at least one semi-crystalline aliphatic polyamide PA1 comprising at least 30%, in particular at least 50% of recycled semi-crystalline aliphatic polyamide PA2 from used or end-of-life pipes for the exploitation of oil or gas fields under the sea or on land, in particular under the sea, said recycled semi-crystalline aliphatic polyamide PA2 having undergone a washing and / or compounding step after removal and grinding in the form of granules from said pipe; (b) from 5 to 50% of at least one reinforcing fiber; (c) from 0 to 40%, in particular from 3 to 30% of at least one impact modifier; d) from 0 to 30%, in particular from 0 to 15% of a load, (e) from 0 to 10%, in particular from 0.1 to 5% of at least one additive, the sum of the components a + b + € + d + e is equal to 100%. In a second embodiment of this first variant, said molding composition according to the invention comprises by weight: a) from 35 to 97%, in particular from 35 to 91.9% of at least one semi-crystalline aliphatic polyamide PAI1 comprising at least 30%, in particular at least 50% of recycled semi-crystalline aliphatic polyamide PA2 from pipes for the exploitation of oil or gas deposits under the sea or on land, in particular under the sea, used or at the end of its life, said recycled semi-crystalline aliphatic polyamide PA2 having undergone a washing and / or compounding step after removal and grinding in the form of granules from said pipe; (b) from 0 to 65%, in particular from 5 to 50% of at least one reinforcing fibre; (c) from 3 to 30% of at least one shock modifier; d) from 0 to 30%, in particular 0 to 15% of a load, (e) from 0 to 10%, in particular from 0.1 to 5% of at least one additive, the sum of the components a + b + € + d + e is equal to 100%. In a third embodiment of this first variant, said molding composition according to the invention comprises by weight: (a) from 35 to 99.9, in particular from 35 to 91.9% of at least one semi-crystalline aliphatic polyamide PA1 comprising at least 30%, in particular at least 50% of recycled semi-crystalline aliphatic polyamide PA2 from used or end-of-life pipes for the exploitation of oil or gas deposits under the sea or on land, in particular under the sea, said recycled semi-crystalline aliphatic polyamide PA2 having undergone a washing and / or compounding step after removal and grinding in the form of granules of said pipe; (b) from 0 to 65%, in particular 5 to 50% of at least one reinforcing fibre; (c) from 0 to 40%, in particular from 3 to 30% of at least one impact modifier; d) from 0 to 30%, in particular 0 to 15% of a load, (e) from 0.1 to 5% of at least one additive, the sum of the components a + b + c + d + e is equal to 100%. Advantageously, in this first variant and its three embodiments, said composition is made up of said constituents. In a second variant, said molding composition comprises by weight: a) from 35 to 92%, in particular from 35 to 91.9% of at least one semi-crystalline aliphatic polyamide PAI1 comprising at least 30%, in particular at least 50% of recycled semi-crystalline aliphatic polyamide PA2 from used or end-of-life pipes for the exploitation of oil or gas deposits under the sea or on land, in particular under the sea, said recycled semi-crystalline aliphatic polyamide PA2 having undergone a washing and / or compounding step after removal and grinding in the form of granules of said pipe; (b) from 5 to 50% of at least one reinforcing fiber; (c) from 3 to 30% of at least one shock modifier; d) from 0 to 30%, in particular from 0 to 15% of a load, €) from 0 to 10%, in particular from 0.1 to 5% of at least one additive, the sum of the components a + c + d + e is equal to 100%. In one embodiment of this second variant, said molding composition according to the invention comprises by weight: a) from 35 to 91.9 of at least one semi-crystalline aliphatic polyamide PAI comprising at least 30%, in particular at least 50% of recycled semi-crystalline aliphatic polyamide PA2 from pipes for the exploitation of oil or gas deposits under the sea or on land, in particular under the sea, used or at the end of their life, said recycled semi-crystalline aliphatic polyamide PA2 having undergone a washing and / or compounding step after removal and grinding in the form of granules from said pipe; (b) from 5 to 50% of at least one reinforcing fiber; (c) from 3 to 30% of at least one shock modifier; d) from 0 to 30%, in particular 0 to 15% of a load, (e) from 0.1 to 5% of at least one additive, the sum of the components a + b + € + d + e is equal to 100%. Advantageously, in this second variant and its embodiment, said composition is made up of said constituents. In a third variant, said molding composition according to the invention comprises by weight: (a) from 35 to 94.9, in particular from 35 to 91.9% of at least one semi-crystalline aliphatic polyamide PA1 comprising at least 30%, in particular at least 50% of recycled semi-crystalline aliphatic polyamide PA2 from used or end-of-life pipes for the exploitation of oil or gas deposits under the sea or on land, in particular under the sea, said recycled semi-crystalline aliphatic polyamide PA2 having undergone a washing and / or compounding step after removal and grinding in the form of granules of said pipe; (b) from 5 to 50% of at least one reinforcing fiber; (c) from 0 to 40%, in particular from 3 to 30% of at least one impact modifier; d) from 0 to 30%, in particular from 0 to 15% of a load, (e) from 0.1 to 5% of at least one additive, the sum of the components a + b + € + d + e is equal to 100%. In one embodiment of these three variants and the embodiments associated with them, said molding composition defined above has a characteristic odor comprising sulfur and / or hydrocarbon and / or aromatic poles according to the description of the field of odors ® by Jean-Noel Jaubert. In one embodiment of these three variations and embodiments associated therewith, said semi-crystalline aliphatic polyamide PAI comprises at least 40% recycled semi-crystalline aliphatic polyamide PA2 from used or end-of-life pipes for the exploitation of oil or gas fields under the sea or on land, in particular under the sea. Advantageously, said semi-crystalline aliphatic polyamide PAI comprises at least 50% of said recycled semi-crystalline aliphatic polyamide PA2. Advantageously, said semi-crystalline aliphatic polyamide PAI comprises at least 60% of said recycled semi-crystalline aliphatic polyamide PA2. Advantageously, said semi-crystalline aliphatic polyamide PAI comprises at least 70% of said recycled semi-crystalline aliphatic polyamide PA2. Advantageously, said semi-crystalline aliphatic polyamide PAI comprises at least 80% of said recycled semi-crystalline aliphatic polyamide PA2. Advantageously, said semi-crystalline aliphatic polyamide PAI comprises at least 90% of said recycled semi-crystalline aliphatic polyamide PA2. In these last six embodiments, said semi-crystalline aliphatic polyamide PAI is made up of said semi-crystalline aliphatic polyamide PA2 in the proportions described. Regarding the reinforcing fibers (b) Regarding the reinforcing fibers, these are short fibers, notably fibers of mineral, organic or vegetable origin. Said reinforcing fiber may be sized or unsized. Said reinforcing fiber can therefore comprise up to 0.1% by weight of a material of an organic nature (thermosetting or thermoplastic resin type) called sizing. Among the fibers of mineral origin, mention may be made of carbon fibers, glass fibers, basalt fibers or basalt-based fibers, silica fibers, or silicon carbide fibers for example. Among the fibers of organic origin, mention may be made of fibers based on thermoplastic or thermosetting polymer, such as semi-aromatic polyamide fibers, aramid fibers or polyolefin fibers for example. Preferably, they are based on amorphous thermoplastic polymer and have a glass transition temperature Tg higher than the Tg of the thermoplastic polymer or polymer mixture constituting the pre-impregnation matrix when the latter is amorphous, or higher than the Tf of the thermoplastic polymer or polymer mixture constituting the pre-impregnation matrix when the latter is semi-crystalline.Among the fibers of plant origin, we can cite natural fibers based on flax, hemp, lignin, bamboo, silk, especially spider silk, sisal, and other cellulosic fibers, in particular viscose. These fibers of plant origin can be used pure, treated or coated with a coating layer, in order to facilitate the adhesion and impregnation of the thermoplastic polymer matrix. Preferably, said reinforcing fiber is chosen from glass fibers, carbon fibers, basalt fibers and basalt-based fibers. More advantageously, said reinforcing fiber is chosen from carbon fibers and glass fibers. In one embodiment, the reinforcing fibers present in a) are glass fibers. Glass fibers can be circular or non-circular in cross-section. A circular cross-section fiber is defined as a fiber having at any point on its circumference an equal distance to the center of the fiber and therefore represents a perfect or near-perfect circle. Any glass fiber that does not have this perfect or near-perfect circle is therefore defined as a fiber with a non-circular section. Examples of non-circular cross-section fibers, but not limited to, are non-circular fibers, such as elliptical, oval, or cocoon-shaped fibers, star-shaped fibers, flake fibers, flat fibers, cruciform fibers, polygonal fibers, and ring fibers. Fiberglass can be: - either with a circular section with a diameter between 4 um and 25 um, preferably between 4 and 15 um. - or with a non-circular section with an L / D ratio (L representing the largest dimension of the cross-section of the fibre and D the smallest dimension of the cross-section of said fibre) of between 2 and 8, in particular between 2 and 4. L and D can be measured by scanning electron microscopy (SEM). Advantageously, the glass fibers are circular. The glass fibers are notably of type E, R, S2, or T. Advantageously the glass fibers are of type E. Regarding the shock modifier (c): The shock modifier is present from 0 to 40%, in particular from 3 to 30% of at least one shock modifier. In one embodiment, it is present from 5 to 20%. For example, impact modifiers are polyolefins with a modulus < 200 MPa, in particular < 100 MPa, as measured according to ISO 178:2010, at 23°C or a thermoplastic elastomer. In one embodiment, the impact modifier is chosen from a polyolefin having a modulus < 200 MPa, in particular < 100 MPa, functionalized or not, and mixtures thereof. Polyolefin: It can be functionalized or non-functionalized or a mixture thereof. For simplicity, the polyolefin has been designated by (B) and poly- functionalized olefins (B1) and non-functionalized polyolefins (B2). 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: - homopolymers and copolymers of polyethylene, in particular LDPE, HDPE, LLDPE (linear low density polyethylene), VLDPE (very low density polyethylene) and metallocene polyethylene. - homopolymers or copolymers of propylene. - ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (abbreviation of ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM), - copolymers of ethylene with at least one product chosen from salts or esters of unsaturated carboxylic acids such as alkyl (meth)acrylate (for example methyl acrylate), or vinyl esters of saturated carboxylic acids such as vinyl acetate (EVA), the proportion of comonomer being able to reach 40% by weight. 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 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. 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: - PE, PP, copolymers of ethylene with propylene, butene, hexene, or octene containing for example 35 to 80% by weight of ethylene; - ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (short 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). - 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; - ethylene vinyl acetate (EVA) and alkyl (meth)acrylate copolymers, containing up to 40% by weight of comonomers. 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). 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. 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: - ethylene / alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers; - ethylene / vinyl acetate / maleic anhydride or glycidyl methacrylate copolymers; - ethylene / vinyl acetate or alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers. In the above copolymers, (meth)acrylic acid can be salified with Zn or Li. 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. Furthermore, the above-mentioned 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 above-mentioned 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. The above-mentioned copolymers, (B1) and (B2), can be copolymerized in a random or block manner and have a linear or branched structure. The molecular weight, MFI index, and density of these polyolefins can also vary widely, as those skilled in the art will appreciate. MFI, short for Melt Flow Index, is the melt flow index. It is measured according to ISO 1133 at 235°C under 5 kg. 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. 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 Lotader® (SK functional polymer) or polyolefins grafted with maleic anhydride such as Orevac® (SK functional polymer) as well as terpolymers of ethylene, alkyl acrylate and (meth)acrylic acid. Homopolymers or copolymers of polypropylene grafted with a carboxylic acid anhydride and then condensed with polyamides or monoamine oligomers of polyamide. In one embodiment, the polyolefin is crosslinked. In another embodiment, the polyolefin is a mechanical blend of a polyethylene or polypropylene matrix olefinic thermoplastic polymer and a vulcanized elastomer such as a vulcanized PP / EPDM blend. Thermoplastic elastomer is a block copolymer (ether-amide block copolymer: PEBA), ether-ester block copolymer, a thermolastic polyurethane: TPU, a thermoplastic styrenic elastomer) Regarding charge (d): The charge is present from 0 to 30%, specifically 0 to 15% of a charge. In one embodiment, the filler is present from 1 to 5%. For example, the fillers may be chosen from silica, graphite, expanded graphite, carbon black, kaolin, magnesia, slag, talc, wollastonite, nanofillers (carbon nanotubes), pigments, metal oxides (titanium oxide), metals, advantageously wollastonite and talc, preferably mainly talc or carbon black. Regarding additives (e) The additive is optional and ranges from 0 to 10.0%, in particular from 0.1 to 5.0% by weight. The additive is chosen from colorants, stabilizers, plasticizers, surfactants, nucleating agents, pigments, brighteners, antioxidants, lubricants, flame retardants, natural waxes, chain extenders, bases and mixtures thereof. Advantageously, the additive is chosen from colorants, stabilizers, plasticizers, surfactants, nucleating agents, pigments, brighteners, antioxidants, flame retardants, natural waxes, chain extenders, bases and mixtures thereof. More advantageously, the additive is chosen from colorants, stabilizers, plasticizers, surfactants, nucleating agents, pigments, brighteners, antioxidants, natural waxes, chain extenders, bases and mixtures thereof. 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 the company Ciba-BASF), a phosphite-type antioxidant (for example irgafos® 126 from the company Ciba-BASF) and possibly other stabilizers such as a HALS, which stands for Hindered Amine Light Stabilizer or hindered amine light stabilizer (for example Tinuvin® 770 from the company Ciba-BASF), a UV stabilizer (for example Tinuvin® 312 from the company Ciba), 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. This stabilizer may 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 associated with alkali metal halides, particularly potassium. 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; hydroxybenzoic acid esters, such as ethyl-2-hexyl parahydroxybenzoate and decyl-2-hexyl parahydroxybenzoate; tetrahydrofurfuryl alcohol esters or ethers, such as oligoethyleneoxytetrahydrofurfuryl alcohol; and citric acid or hydroxymalonic acid esters, such as oligoethyleneoxy malonate. It would not be outside the scope of the invention to use a mixture of plasticizers. Examples of bases used are zinc or calcium stearates, potash (KOH), sodium hydroxide (NaOH), and magnesium and calcium carbonates. In one embodiment, the composition according to the invention contains less than 5%, advantageously less than 2%, of plasticizer. In another embodiment, the composition has an MFI measured according to the ISO 1133 standard at 235°C under 5 kg of between 0.5 and 25. In yet another embodiment, the inherent viscosity of said composition, as determined according to ISO 307:2007 in m-cresol at 20°C, is less than or equal to 1.6 dl / g, in particular between 0.8 dl / g and 1.4 dl / g. According to another aspect, the present invention relates to a process for preparing a recycled semi-crystalline aliphatic polyamide as defined above, characterized in that it comprises, after removal and grinding in the form of granules from used pipes or at the end of the life of an oil or gas deposit exploitation platform under the sea or on land, in particular under the sea, a step of washing and / or compounding said semi-crystalline aliphatic polyamide PA2. According to another aspect, the present invention relates to the use of a composition as defined above, for preparing articles obtained by extrusion. According to yet another aspect, the present invention relates to a method for preparing a single-layer or multi-layer pipe, characterized in that it comprises a step of molding a composition as defined above. Description of figures [Fig.1] presents the field of odors® by Jean-Noel Jaubert The meaning of the abbreviations used in [Fig.1] is presented in Table 1. [Fig.2] [Fig.2] shows the setup for performing the laser welding described in Table 2. [Tables 1] AC= Cynnamyl alcohol |ax= Ambroxan® BZ = Benzyl acetate AM= Iso- bu- tylamine BA= Benzaldehyde te |CA=Calone® AB= Am- AC= Cynnamyl AM= Isobu- AN= Methylan- brettolide® alcohol tylamine thralylate AP= Phenethyl |ax= Ambroxan® BA= Ben- BE= Ethyliso- alcohol zaldehyde butyrate BU= Acid BZ= Benzyl acetate_ |CA= Calone® CD= Cinna- butyric maldehyde CI=Citral CL= Hypochlorite CM= Camphor (CO= Coumarin CR= B- CY= Methyl sa- DC= Y- DI= Diacetyl caryophyllen licylate undecanolactone EG= Eugenol |EM= Ethylmaltol EV= Evenyl GE= Geosmine |HX= cis-3-hexenol |[M=d-imonem | |LN=Linalool | |ME=1-menthol MT= Methional NO= Nonanal OC= 1-octene-3-o1 |OL= trans-anethole PA= Ethypheny- |PB= p- PH= Phenom PI= a-pinene lacetate hydroxyphenylbutano ne PN= cyclo- PY= QU= Isobutyl- SA= Diallyl pentanone 2-acetylpyrazine quinoline disulfide SC= Skatole SM= dimethyl TE= Terpinyl |TH= Thymol disulfide acetate |va= Vanillin VE= Vetiveryl acetate EXAMPLES The invention will now be described in more detail with the aid of the following examples which are not limiting. The different compositions used for the preparation of the plates of the invention are as follows: Virgin PAI1 = PA1I of Mn 28,000 g / mol + 1% thermal stabilizer (consisting of 0.7% of Lowinox® 44B25 phenol from Great Lakes, 0.3% of Irgafos® 168 phosphite from Ciba). Virgin PA12 = PA12 of Mn 26,000 g / mol + 1% thermal stabilizer (consisting of 0.7% of Lowinox® 44B25 phenol from Great Lakes, 0.3% of Irgafos® 168 phosphite from Ciba). PAI1I1 Recyl = composition made up of 100% PA11 from offshore pipe crushed into particles ranging in size from 0.5mm to 25mm. PAII Recy2 = composition consisting of 100% PA1I from offshore pipe crushed into particles ranging in size from 0.5mm to 25mm then washed with methanol by dissolution reprecipitation. PAI1 recy3= composition consisting of 50% PA11 from offshore pipe crushed into particles ranging in size from 0.5mm to 25mm then washed with methanol by dissolution reprecipitation then compounded with 50% virgin PA 11. PAII recy4= composition consisting of 45% PAII from offshore pipe ground into particles of size ranging from 0.5mm to 25mm then washed with methanol by dissolution reprecipitation then compounded with 4.5% virgin PA11, 50% circular section E-glass fiber supplied by Lanxess, 0.5% antioxidants (consisting of 0.35% Lowinox® 44B25 phenol from Great Lakes, 0.15% Irgafos® 168 phosphite from Ciba). PA12 recy5= composition consisting of 70% PA12 from offshore pipe ground into particles ranging in size from 0.5mm to 25mm then washed with methanol by dissolution reprecipitation then compounded with 20% virgin PA12, 9.5% Orevac® IM800 impact modifier marketed by SK FP, 0.5% antioxidants (consisting of 0.35% Lowinox® 44B25 phenol from Great Lakes, 0.15% Irgafos® 168 phosphite from Ciba). The compositions PA 1 lrecy3, PA11 recy4 and PA125 recy were prepared by conventional compounding in a co-rotating twin-screw extruder of the Coperion® 40 type, 70kgh, at 300rpm, at 270°C. The compositions were then molded on an injection molding machine (Engel) at a set temperature of 240°C for the feed and 260°C for the nozzle and a mold temperature of 60°C in the form of 100x100x1 mm°* plates for exudation measurements. 50x50x2mm? plates are produced for laser welding tests. The injected plates above were then evaluated on several criteria: The results are shown in Table 2. [Tables 2] Sample|Exudation after our injection and [Low (1) s |Laser welding on injected plates Shear stress 0 (MPa) 5 |Weak d) |s qe |BC1 |PA12 virgin |BC2 |PAI1 virgin EC3 |PA 11 Recyl [Er |A 11 [Weak (1) 13 |E1 [PA It [Weak (1) [12 + oil) 11 |PA11 |Low (1) Recy2 1 |PA 11 |Low (1) Recy3 |E13 |Low (1) [17 |E14 [PA l [Low (1) [14 3 |[PAI Recy4 4 |PA1I2 Recy Exudation is manifested by the appearance of a deposit on the surface and is estimated visually. Plaques are graded from 1 (little exudation) to 5 (much exudation) by trained personnel. The samples used for welding tests are 40x10x2mm° samples obtained from 5S0x50x2mm injected parts. The samples were cut using a pneumatic press and a die cutter. The materials EC2, EC3, EC4, ECS, EI and EI2 will be welded to the reference material: EC2. The materials EC1 and FI3 will be welded to the reference material: EC1 The welding is carried out using an LPKF Inlineweld 6200 machine (Garben, Germany) using a spot diameter of 2.1mm and a clamping force of 700N. Infrared radiation is produced using a laser diode with a wavelength of 980nm. For each sample, the laser power is 110W and the welding speed is 1000 mm / s. The quality of the weld is defined by a mechanical test of the two welded parts according to ASTM D3164-03. This measures the shear stress indicated in Table 2. The compositions of the invention exhibit the best compromise between exudation and shear stress. In particular, the shear stress of the compositions of the invention is higher than that of the comparative compositions EC1 and EC2 and the exudation of the compositions of the invention is lower than that of the comparative composition EC3.

Claims

Claims

1. A molding composition comprising by weight: a) from 35 to 100%, in particular from 35 to 91.9% of at least one polyamide semi-crystalline aliphatic PA] comprising at least 30%, in par- in particular at least 50% recycled semi-crystalline aliphatic polyamide PA2 from oil or gas field exploitation pipes under the sea or on land, especially under the sea, used or at the end of life, said recycled semi-crystalline aliphatic polyamide PA2 having undergone a washing and / or compounding step after removal and grinding under granule form of said pipe; (b) from 0 to 65%, in particular 5 to 50% of at least one reinforcing fibre; (c) from 0 to 40%, in particular from 3 to 30% of at least one impact modifier; d) from 0 to 30%, in particular 0 to 15% of a load, (e) from 0 to 10%, in particular from 0.1 to 5% of at least one additive, the sum of components a + b + c + d + e is equal to 100%.

2. Molding composition according to claim 1, characterized in that recycled semi-crystalline aliphatic polyamide PA2 is a polyamide with long chain with an average number of carbon atoms per nitrogen atom greater than 7, in particular greater than 9.

3. A molding composition according to either of claims 1 or 2, ca- characterized in that said recycled semi-crystalline aliphatic polyamide PA2 comprises at least one species selected from the compounds sulfur, alkanes, aliphatic mono acids from C14 to C18, mono- or poly-aromatic compounds and aromatic acids.

4. Molding composition according to one of claims 1 to 3, ca- characterized in that said recycled semi-crystalline aliphatic polyamide PA2 comprises at least one species selected from alkanes, mono aliphatic acids from C14 to C18, mono or poly- compounds aromatics and aromatic acids.

5. Molding composition according to one of claims 1 to 4, ca- characterized in that said recycled semi-crystalline aliphatic polyamide PA2 comprises at least one species selected from alkanes, mono- or poly-aromatic compounds and aromatic acids.

6. Molding composition according to one of claims 1 to 5, ca- characterized in that said recycled semi-crystalline aliphatic polyamide PA2 comprises at least one species selected from alkanes such as methylcyclopentane, cyclohexane, methylcyclohexane, 1,2-cis-dimethylcyclohexane, 1,2-trans-dimethylcyclohexane, 1,3-cis-dimethylcyclohexane, 1,3-trans-dimethylcyclohexane, 1,4-cis-dimethylcyclohexane, 1,4-trans-dimethylcyclohexane, or ethylcyclohexane and mono or polyaromatic compounds such as toluene, xylene, trimethylbenzene, diphenyl methyl and diphenyl methanol, naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, 1,2-dimethylnaphthalene, 1,3-dimethylnaphthalene, 1,4-dimethylnaphthalene, 1,3,6-trimethylnaphthalene, 2,3,5-trimethylnaphthalene, 1-phenanthrene, 2-methyl phenanthrene.

7. Molding composition according to one of claims 3 to 6, ca- characterized in that the mass content of said species present in the recycled semi-crystalline aliphatic polyamide PA2 is comprised of 100 ppm to 2000 ppm, especially from 100ppm to 1000ppm

8. Molding composition according to one of claims 1 to 7, having a characteristic odor including sulfur poles / pyrogenic and / or hydrocarbons and / or aromatic, terpenic and phenolic.

9. Molding composition according to one of claims 1 to 8, ca- characterized in that the recycled semi-crystalline aliphatic polyamide PA2 presents functions resulting from thermolysis reactions in an acid medium in particular amide functions and / or methylene in alpha of said amide functions and acid chain ends, chosen from nitrile functions, ketones, and ester functions resulting from the reaction of acid functions of polyamide with alcohols used during life of said pipes, in a molar ratio relative to the amide functions higher than that of the same polyamide constituting an unused pipe.

10. Molding composition according to claim 9, characterized in that the molar ratio of the functions resulting from thermolysis reactions is comprised from 1 / 10000 to 1 / 20 as determined by proton NMR.

11. | Molding composition according to one of claims 1 to 10, ca- characterized in that the recycled semi-crystalline aliphatic polyamide PA2 includes a rate of cyclic oligomers chosen from oligomers having a molar mass less than 1000 g / mol less than that of the virgin polyamide equivalent.

12. Molding composition according to one of claims 1 to 11, ca- characterized in that the recycled semi-crystalline aliphatic polyamide PA2 includes a rate of alkyl chain ends, ranging from 1 ppm to 5000 ppm, advantageously 10 to 2500 ppm, said alkyl being C1 to C18 and said rate being higher than that of a semi-aliphatic polyamide virgin crystalline.

13. Process for the preparation of a semi-crystalline aliphatic polyamide recycled as defined in one of claims 1 to 12, characterized in which it includes, after removal and grinding in the form of granules of used or end-of-life pipes from oilfield exploitation platforms of oil or gas under the sea or on land, in particular under the sea, a step of washing and / or compounding said aliphatic polyamide semi-crystalline PA2.

14. Use of a composition as defined in one of the claims- dications 1 to 12, for preparing articles obtained by injection.

15. Process for preparing a single-layer or multi-layer pipe, ca- characterized in that it comprises a step of molding a composition as defined in one of claims 1 to 12.