On- and offshore long-chain polyamide tube with increased barrier effect

Abstract

The invention relates to multilayer hollow bodies, in particular multilayer polyamide tubes, with increased barrier effect relative to H2 permeation.

Description

On- and offshore long-chain polyamide pipe with improved barrier effect [1] The invention relates to a multilayer hollow body which, through the selection of the molding compounds used in its individual layers, exhibits reduced permeation of, for example, hydrogen (Hz), HzS, CO₂ and CH₄, with the reduction of hydrogen (Hz) permeation being preferred. The multilayer hollow body is primarily a hollow profile, such as a pipe, or a container for conveying or storing liquid or gaseous media. [2] Multilayer hollow bodies are used in particular as offshore or onshore pipes, or as a section of a corresponding offshore or onshore pipeline. An offshore pipe is usually laid on or below a body of water in a trench, while an onshore pipe is laid on land. Offshore and onshore pipes can be combined to form pipelines that transport liquid or gaseous media over long distances both underwater and on land. Known offshore and onshore pipes are typically made of steel. [3] With the increasing politically driven focus of the primary energy sector on renewable and climate-neutral energy sources or the transmission and storage of greenhouse gases, conventional steel pipe infrastructure is coming under intense scrutiny for safety considerations. Hydrogen embrittlement (HE) of austenitic steels and welded joints is a particular issue that requires increased technical effort to address, especially when the lower energy density of hydrogen (Hz) compared to natural gas / methane has to be compensated for by higher pressures. This requires systems that meet the demands placed on Hz permeation, which are not met by conventional pipe materials. [4] Hydrogen embrittlement refers to the change in the strength of metals, more precisely their brittleness, caused by the penetration and incorporation of hydrogen (Hz) into their metal lattice. This corrosion is similar to material fatigue. As a result, hydrogen-induced cracking occurs, which in particular limits the use of susceptible materials for hydrogen storage and / or hydrogen transmission. [5] Multilayer hollow bodies, in particular pipes, are known from the prior art which are provided with a metallic barrier layer, for example made of aluminium, for protection against hydrogen, which involves increased manufacturing and material costs. Such pipes are known, for example, as polymer composite pipes and reinforced thermoplastic pipes (RTPs). [6] Furthermore, with these known multilayer hollow bodies, there is a risk of a ‘cover blow-off’ at very high pressures, since the aluminum winding layers allow permeation of Hz under the unwelded polymer covering over a long period of time due to the so-called ‘tortoise effect’, resulting in a partial pressure of Hz there over time. This can lead to the loss of the covering of the hollow body. [7] RTPs are only used in higher pressure ranges and currently only onshore. [8] Furthermore, thermoplastic composite pipes (TCPs) are known. These are reinforced composite multilayer pipes where there is no risk of cover blow-off. Although the Hz permeation is reduced, it is not as low as with unbonded onshore RTPs with an aluminum layer. [9] The hollow bodies known from the prior art are therefore not satisfactory in every respect.

[0010] It is therefore an object of the present invention to provide hollow bodies which have advantages over the known hollow bodies.

[0011] This problem is solved by the subject matter of the patent claims.

[0012] It was surprisingly found that, in the "onshore unreinforced up to 18 bar" range, manufacturing and cost advantages can be achieved compared to RTPs using multilayer hollow bodies produced by co-extrusion according to the invention. Furthermore, in the onshore range, Hz embrittlement can be avoided compared to steel.

[0013] It was surprisingly found that an even better blocking effect can be achieved in the offshore area for TCPs qualified on a PA 12 basis.

[0014] It was also surprisingly found that, via an ethylene-vinyl alcohol copolymer (EVOH) barrier layer in a multilayer tube batch with adhesion promoter based on polyamide (PA), in particular PA 6 and PA 6.12 (i.e. PA6 / PA612 mixture), high molecular weight, chain-extended large tube extrusions or polyamide-based moldings, in particular PA 12, can be optimized with regard to Hz permeation in the co-extrusion process.

[0015] It was also surprisingly found that a pipe assembly functions mechanically even with a significantly off-center arrangement of the EVOH barrier layer, e.g., as the innermost layer in direct interaction with Hz. Normally, this layer is located very centrally in small pipes.

[0016] It was also surprisingly found that the adhesion mechanism of the PA6- and PA612-based adhesion promoter composition works remarkably well with chain-extended PA compounds / polyamides. It is particularly noteworthy that, depending on the composition, no compatibilization is necessary.

[0017] The use of the chain-extended PA 12 compounds in combination with an EVOH barrier layer enables the transport of ua Hz currents in an advantageous manner, particularly with regard to reduced Hz permeation.

[0018] In particular, the invention enables, for the first time, large-diameter on- and offshore polyamide pipes for diverse applications in unreinforced systems for l-ready applications (MOP 16 or 18 bar) onshore, up to 100% green F reinforced pipes (thermoplastic composite pipes (TCP) and reinforced thermoplastic pipes (RTP)) for higher pressure ratings offshore applications. MOP stands for "maximum operating pressure." This is the maximum permissible operating pressure at which a system can be operated continuously under normal operating conditions.

[0019] Polyamides are not inherently sensitive to helium. This eliminates helium from the outset, as well as "conventional" corrosion. The requirement to prevent hydrogen permeation into the environment is demonstrably met by the functionality of the EVOH barrier layer. The relevant context is "secondary greenhouse gas emissions." Hydrogen is indirectly harmful to the climate because it stabilizes other directly acting greenhouse gases, such as methane (CH4) and carbon dioxide (CO2), in the atmosphere for longer periods and thus at higher concentrations. There will be political efforts toward "zero-permeation solutions."

[0020] Even the geometric design with a very thin EVOH barrier layer (~0.3 mm) at an overall diameter of 50 mm and larger, and wall thicknesses of 3 mm and greater, surprisingly ensures mechanical system performance similar to a monotube, while drastically reducing H₂ permeation. EVOH barrier layers smaller than 0.3 mm, such as a layer thickness of 0.1 mm, also significantly reduce H₂ permeation compared to a monotube. Thicker layers (up to 0.8 mm) were also investigated, but no differences in mechanical performance could be determined.

[0021] Another potential benefit lies in the transport of supercritical CO2, which poses a significant problem for steel. Further applications include the conveying of multiphase fluids with high barrier requirements (H2S, CO2, CH4, etc.).

[0022] Furthermore, the multi-layered hollow body is easy to process and can be wound, especially in industrially relevant diameters.

[0023] According to the invention, pipe structures can thus be designed more flexibly and the arrangements and geometries of the EVOH barrier layer can be optimized depending on the pipe structure or the other layers.

[0024] The multilayer hollow body according to the invention also makes it possible to take into account the special requirements for the molding compounds with regard to the layer thickness-diameter ratio of the coextrusion process used for their production: melt stiffness on the one hand; residence times; adhesion; small volume EVOH barrier layer plus small volume adhesion promoter layer plus large volume PA support layer (12, 6.12, etc.).

[0025] Figure 1 illustrates the Fb permeability of selected polymers and of PA 12-EVOH-MLT- Systems.

[0026] Figure 2 illustrates the PA 12-EVOH-MLT-TCP approach for 100% Fh high pressure for offshore applications.

[0027] Figure 3 illustrates the PA 12-EVOH gaspipe approach for 16 or 18 bar MOP for onshore applications.

[0028] Figure 4 shows a welded test specimen.

[0029] Figure 5 illustrates tensile strength properties of welded specimens compared to non-welded specimens for single- and multi-layer pipes.

[0030] Figure 6 illustrates investigations of the flushability of an MLT pipe with an internal EVOH barrier layer.

[0031] The invention relates in a first aspect to a multi-layered hollow body, in particular for the transport, transmission, distribution and / or storage of gases and / or liquids, which has or consists of the following layers from the inside out: - optionally a layer I comprising or consisting of a molding compound containing polyethylene (PE), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), poly(tetrafluoroethylene-perfluoromethyl vinyl ether) (MFA), fluoroethylene propylene (FEP) and / or ethylene chlorotrifluoroethylene (ECTFE); and preferably comprising or consisting of PE-HP, PVDF-HP, PFA-HP, MFA-HP and / or FEP-HP (HP = high purity); - optionally a layer II, which is an adhesion promoter layer and contains or consists of a molding compound PA 6, PA 6.12, its copolymers and / or mixtures thereof; - a barrier layer (layer III) comprising or consisting of a molding compound containing ethylene-vinyl alcohol copolymer (EVOH); - an adhesion promoter layer (layer IV) comprising or consisting of a molding compound containing PA 6, PA 6.12, its copolymers and / or mixtures thereof; - a layer V comprising a molding compound containing at least one chain-extended polyamide; and preferably chain-extended PA 12, chain-extended PA 6.12, chain-extended bio-PA, its copolymers and / or mixtures thereof, wherein the chain-extended polyamides are obtainable by means of a chain-extending additive having at least 2 carbonate units per molecule; optionally a layer VI comprising or consisting of a molding compound containing carbon fiber reinforced PA 12; and - possibly a layer VII, which is a protective coating.

[0032] The multi-layered hollow body is preferably configured for the transport, transmission, distribution and / or storage of gases and / or liquids.

[0033] Layer I or layer II is in direct contact with the transported or stored medium, preferably H2.

[0034] The barrier layer (layer III) acts as a barrier, particularly against Hz permeation. In the absence of layers I and II, layer III is in direct contact with the conveyed or stored medium, preferably H2.

[0035] High-purity inner layers are characterized by the fact that, in contact with the media, the media can only leach out marginal components ("extractables") from the inner layer. Furthermore, these extremely low levels of leachout are negligible with regard to the high purity of the medium being transported and its intended use.

[0036] The expert is able to determine an acceptable level of leaching on a case-by-case basis.

[0037] For example, a specialist is able to determine an acceptable level of impurities in the hydrogen (H2) in connection with a fuel cell, which does not impair the functionality of the fuel cell.

[0038] Preferably, the multilayer hollow body has a gas permeability (G), preferably permeability of H2, in a temperature range of 20 to 100 degrees Celsius of at most 200 or at most 300 or at most 400 or at most 500 or at most 1000 cm 3 / m 2 * d * bar on, preferably each determined according to DIN 53380, Part 1.

[0039] Preferably, the barrier layer (layer III) has a gas permeability (G), preferably permeability of H2, in a temperature range of 20 to 100 degrees Celsius of at most 200 or at most 300 or at most 400 or at most 500 or at most 1000 cm⁻¹. 3 / m 2* d * bar on, preferably each determined according to DIN 53380, Part 1.

[0040] If the hollow body according to the invention has a layer VI which comprises or consists of a molding compound containing carbon fiber reinforced PA 12, this is preferably a unidirectionally (UD) fiber-reinforced continuous strip which preferably has a carbon fiber content of 40 to 50 volume% and a low-viscosity PA 12 content of 40-60 These unidirectional fiber-reinforced continuous tapes preferably have a carbon fiber content of approximately 45% by volume and a low-viscosity PA 12 content of approximately 55% by volume. The carbon fibers preferably have a diameter of 4–15 mm, particularly preferably 7–12 mm. The PA 12 preferably has a melt viscosity in the range of 10 to 100 Pa s, measured with an Anton-Paar rheometer type MCR 502 with a plate-plate system (plate spacing d = 25 mm), at a rotational frequency of 1000 rpm, at a temperature of 280°C.

[0041] Preferably the (wall) thickness of layer III is - at least 0.2 mm or at least 0.3 mm or at least 0.4 mm or at least 0.5 mm; and / or - at most 0.6 mm or at most 0.7 mm or at most 0.8 mm or at most 0.9 mm or at most 1.0 mm.

[0042] Preferably the (wall) thickness of layer IV is - at least 0.1 mm or at least 0.12 mm or at least 0.15 mm or at least 0.17 mm; and / or - at most 0.2 mm or at most 0.22 mm or at most 0.24 mm or at most 0.30 mm or at most 0.5 mm.

[0043] Preferably the (wall) thickness of layer V is - at least 5.0 mm or at least 6.0 mm or at least 7.0 mm or at least 8.0 mm or at least 9.0 mm; and / or - at most 10.0 mm or at most 11.0 mm or at most 12.0 mm or at most 13.0 mm or at most 15.0 mm.

[0044] Methods for determining suitable (wall) thicknesses are known to experts, e.g. the calculation using the "kettle formula".

[0045] Preferably, the (wall) thicknesses are determined according to the standard DIN EN 13480-3:2017-12.

[0046] Preferably the inner diameter (i.e., diameter without taking the layers into account) of the multilayer hollow body according to the invention, in particular the onshore and / or offshore pipe, is at least 30 mm or at least 50 mm and / or at most 160 mm or at most 300 mm or at most 350 mm.

[0047] The multilayer hollow body according to the invention can have the same or different polyamides (PA) in different layers. Such polyamides and the abbreviations used to designate them are known to those skilled in the art.

[0048] A polyamide particularly suitable for the purposes of the invention is based on lactams, aminocarboxylic acids (perlon type), diamines or dicarboxylic acids (nylon type). It can Furthermore, they contain branching building blocks derived, for example, from tricarboxylic acids, triamines, or polyethyleneimine. Suitable types, either as homopolymers or copolymers, include, for example, PA 6, PA 4.6, PA 6.6, PA 6.10, PA 6.6 / 6, PA 6 / 6T, PA 6.6 / 6T, and in particular PA 6.12, PA 10.10, PA 10.12, PA 12.12, PA 6.13, PA 10.14, PA 11, PA 12, or a transparent polyamide.

[0049] For example, the following are suitable for transparent polyamides: - the polyamide made from terephthalic acid and the isomer mixture of 2,2,4- and 2,4,4-trimethylhexamethylenediamine, - the polyamide made from isophthalic acid and 1,6-hexamethylenediamine, - the copolyamide consisting of a mixture of terephthalic acid / isophthalic acid and 1,6-hexamethylenediamine, - the copolyamide of isophthalic acid, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane and laurinlactam or caprolactam, - the (co)polyamide of 1,12-dodecanedioic acid, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane and optionally laurinlactam or caprolactam, - the copolyamide of isophthalic acid, 4,4'-diaminodicyclohexylmethane and laurinlactam or caprolactam, - the polyamide of 1,12-dodecanedioic acid and 4,4'-diaminodicyclohexylmethane, and / or - the copolyamide consisting of a terephthalic acid / isophthalic acid mixture, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane and laurinlactam.

[0050] Furthermore, polyetheramides based on lactams, aminocarboxylic acids, diamines, dicarboxylic acids and polyetherdiamines and / or polyetherdiols are suitable.

[0051] PA 6 is preferably produced by ring-opening polymerization of caprolactam.

[0052] PA 11 is preferably prepared by polycondensation of γ-aminoundecanoic acid, while PA 12 is obtained by ring-opening polymerization of laurinlactam. Both polymers are commercially available in a variety of grades.

[0053] PA 6.10 is preferably prepared in a known manner by polycondensation of an equivalent mixture of hexamethylenediamine and 1,10-decanedioic acid, while PA 6.12 is preferably prepared in a known manner by polycondensation of an equivalent mixture of hexamethylenediamine and 1,12-dodecanedioic acid, and PA 10.10 is preferably prepared in an equally known manner by polycondensation of an equivalent mixture of 1,10-decanediamine and 1,10-decanedioic acid.

[0054] PA 10.12 is preferably prepared by polycondensation of an equivalent mixture of 1,10-decanediamine and 1,12-dodecanedioic acid, while PA 12.12 is obtained in the same way from 1,12-dodecanediamine and 1,12-dodecanedioic acid.

[0055] PA 6.6 is preferably produced by polycondensation of hexamethylenediamine and adipic acid. Like PA 6, it is commercially available in a wide variety of grades.

[0056] PA 6 / 6.6 is a copolycondensate starting from the monomers caprolactam, hexamethylenediamine and adipic acid.

[0057] Preferably, mixtures of different polyamides are used, e.g. PA 12 / PA 10.12 or PA 12 / PA 12.12. Such mixtures are characterized by a particularly high low-temperature impact strength; they are described, for example, in EP-A-0 388 583.

[0058] Bio-PA is a polyamide based on renewable raw materials. The monomers are preferably obtained wholly or partially from castor oil.

[0059] Preferably, at least one layer contains a polyamine-polyamide copolymer.

[0060] The polyamine-polyamide copolymer is preferably prepared using the following monomers: a) 0.5 to 25 wt.%, preferably 1 to 20 wt.% and particularly preferably 1.5 to 16 wt.%, based on the polyamine-polyamide copolymer, of a polyamine having at least 4, preferably at least 8 and particularly preferably at least 11 nitrogen atoms and a number-average molecular weight Mn of at least 146 g / mol, preferably of at least 500 g / mol and particularly preferably of at least 800 g / mol, and b) polyamide-forming monomers selected from lactams, ω-aminocarboxylic acids and / or equimolar combinations of diamine and dicarboxylic acid.

[0061] In a preferred embodiment, the amino group concentration of the polyamine-polyamide copolymer is in the range of 100 to 2500 mmol / kg.

[0062] These and other suitable polyamine-polyamide copolymers and methods for their production are known to experts, for example, from publication EP-A-3 299 165.

[0063] In a preferred embodiment, the multilayer hollow body does not contain layer I, or does not contain layer I and layer II, and layer III is both a barrier and an inner layer.

[0064] Layer V comprises a molding compound containing at least one chain-extended polyamide.

[0065] Exemplary methods for chain lengthening are defined below.

[0066] In a preferred embodiment, the molding compound of layer V is obtained by condensing a PA12, PA612 and / or bio-PA molding compound with a compound having at least two carbonate units and the polyamide content of the PA12, PA612 and / or bio-PA. The molding compound contains at least 5 ppm phosphorus in the form of an acidic compound due to the manufacturing process, wherein a) 0.001 to 10 wt%, based on the polyamide, of a salt of a weak acid is added to the polyamide before or during compounding, and b) a mixture of the finished compound and 0.005 to 10 wt%, based on the polyamide, of the compound with at least two carbonate units is prepared.

[0067] In a preferred embodiment - the polyamide component contains 20 to 500 ppm phosphorus in the form of an acidic compound; and / or - 0.001 to 5 wt.%, preferably 0.01 to 2.5 wt.%, particularly preferably 0.05 to 1 wt.%, of a salt of a weak acid is added to the polyamide, and the weak acid preferably has a pKa value of 2.5 or higher and / or the salt of the weak acid is preferably an alkali metal salt, an alkaline earth metal salt, the salt of a metal of group III, the salt of a metal of group II, or an ammonium salt; and / or - was the polyamide manufactured using a diamine or polyamine as a regulator; and / or - the compound with at least two carbonate units is used as a masterbatch.

[0068] Experts know how the terms polyamides can be defined and synthesized. This is done using so-called regulators. In the case of nylon-type polyamides, this can be a simple stoichiometric excess of one of the two components. Alternatively, an external regulator can be added; this can be done for both polyamide types (Perlon and Nylon). These regulators can be, for example, diamines or diacids, which are essential for polyamide formation.

[0069] In principle, the methods for determining the end groups of polyamides are known to experts. The determination of carboxyl end groups is preferably carried out by dissolving the polymer in benzyl alcohol and alkalimetric titration with alcoholic KOH (0.1 mol / L standard solution) against phenolphthalein. The determination of amino end groups in m-cresol is preferably carried out by dissolving the polyamide at elevated temperature. The endpoint is indicated potentiometrically.

[0070] If the polyamide was produced using a diamine or polyamine, it can be obtained with an excess of amino end groups. The amino end group concentrations can preferably be determined by potentiometric titration. For this purpose, for example, 0.2 to 1.0 g of polyamide are dissolved in a mixture of 50 ml m-cresol and 25 ml isopropanol at 50 to 90 °C and, after the addition of aminocaproic acid, titrated with a 0.05 M perchloric acid solution.

[0071] These and other possibilities for the production of chain-extended polyamides are known to experts from publication EP 1 690 890 A1.

[0072] In a preferred embodiment, the molding compound of layer V contains a viscosity modifier (i.e., an additive) which, during thermoplastic processing, leads to an increase in molecular weight through chain extension of polyamide molecules. A preferred variant of a viscosity modifier is a polycarbonate in an acid-terminated polyamide. Such a viscosity modifier is commercially available, for example, under the name Brüggolen® M 1251 (trademark of Brüggemann GmbH & Co. KG, Germany) from Brüggemann Chemical (Germany), which is a masterbatch of a low-viscosity polycarbonate in an acid-terminated polyamide 6.

[0073] Such Brüggolene® are able to react during extrusion with amine-controlled polyamide, e.g. amine-controlled PA 12, so that the polymer chain is lengthened and the molar mass increases.

[0074] When reacting an amine-controlled polyamide, e.g. amine-controlled PA 12, with a Brüggolen®, e.g. Brüggolen® M 1251, the proportion of Brüggolen® is preferably less than 2 wt.%, based on the total weight of the amine-controlled polyamide and the Brüggolen®.

[0075] In a preferred embodiment, the molding compound of layer V contains or consists of chain-extended PA of the following formulas:

[0076] Further methods for chain extension are known to experts from publications WO 2000 / 066650, EP 2 687 554 A1 and EP 2 610 279 A1.

[0077] In a preferred embodiment, a chain-extending additive such as carbonyl bis-caprolactam (CBC), N-N'-terephthaloyl bis-caprolactam, bisoxazolines, diisocyanates, disguised diisocyanates, carbodiimides, is added to the polyamides, in particular to the polyamides of layer V. Epoxy-functionalized 5 oligo- or polymer- or carbonate unit-based additives.

[0078] The preferred chain-extending additives have at least 2 carbonate units per molecule, preferably 5, more preferably 10, further more preferably 20, particularly preferably 30, more particularly preferably 40 and particularly preferably at least 50 carbonate units per molecule.

[0079] Particularly preferred chain-extending additives are disclosed in WO 2000 / 066650, in particular preferred are chain-extending additives such as block copolymers of the formula PA.PC, where PA means polyamide and PC means polycarbonate.

[0080] The polycarbonate has at least 2 carbonate units, preferably 10, more preferably 20, further preferably 30, particularly preferably 40 and in particular at least 50. Preferably the polycarbonate has 2 to 100, particularly preferably 30 to 80 and in particular preferably 40 to 70 carbonate units.

[0081] The chain extender is present in a materbatch of acid-terminated polyamide and is reacted with an amine-terminated polyamide.

[0082] The chain-extending additive preferably contains 25 to 75 wt.%, more preferably 35 to 65 wt.% and particularly preferably 45 to 55 wt.% of polycarbonate.

[0083] Such methods for chain extension of polyamides are known to those skilled in the art from publications EP 1 690 890 A1 , WO 01 / 53382 A1 and WO 01 / 66643 A1.

[0084] In a preferred embodiment, the following - layers I, II, III, IV and V, or - layers I, II, III, IV, V, VI and VII, or - layers III, IV and V, or - layers III, IV, V, VI and VII directly on top of each other; and / or - Layer III is arranged off-center.

[0085] According to the invention, "arranged off-center" means that, starting from the off-center layer, the number of layers inwards, i.e., towards the transported medium, does not correspond to the number of layers outwards. Therefore, according to the invention, several layers of a multilayer hollow body can also be arranged off-center.

[0086] In a preferred embodiment, the molding compound of layer V contains additional polyamides, their copolymers and / or mixtures thereof, - vorzugsweise PA 8, PA 9, PA 10, PA 11, PA 12, PA 4.6, PA 6.10, PA 6.12, PA 6.13, PA 6.14, PA 6.16, PA 8.10, PA 8.13, PA 9.10, PA 9.12, PA 10.10, PA 10.12, PA 10.14, PA 10.16, PA 10.18, PA 12.12, PA DACH.6 (Diaminocyclohexan), PA DACH.10, PA DACH.12, PA DACH.10 / 11, PA PACM.6 (4,4-Diaminodicyclohexylmethan), PA PACM.10, PA PACM.12, PA MACM.6 (3,3'-Dimethyl-4,4'-diaminocyclohexylmethan), PA MACM.10, PA MACM.12,. PA 6.T (T = Terephthalate), PA 9.T, PA 10.T, PA 12.T, PA 6.I (I = Isophthalate), PA 9.I, PA 10.1, PA 12.1, PA 6.N (2,6-Naphthalindicarbonate), PA 10.N, PA 12.N, PA MXD.6 (MXD = meta-Xyloldiamin), PA MXD.10, PA MXD.12, PA IPD.6 (Isophorondiamin), PA IPD.10, PA IPD.12, PA IND.6 (Isononyldiamin, 1,6-Diamino-2,4,4-trimethylhexane), PA IND.10, PA IND.12, PA ND.6 (Nonyldiamin, 1,6-Diamino-2,2,4- trimethylhexan), PA ND.10, PA ND.12, deren Copolymeren und / oder Mischungen davon.

[0087] In einer bevorzugten Ausführungsform - contains the molding compound of layer I PE-HP, PVDF-HP, PFA-HP, MFA-HP and / or FEP-HP, each individually or in total in an amount of at least 80 wt.%, preferably at least 85 wt.% and particularly preferably at least 90 wt.%, in each case based on the total weight of layer I and / or the molding compound of layer I; and / or - The molding compound of layer V contains chain-extended PA 12, chain-extended PA 6.12, chain-extended bio-PA, their copolymers and / or mixtures thereof, each individually or in total in an amount of at least 50 wt.%, preferably at least 60 wt.%, particularly preferably at least 65 wt.% and especially preferably at least 70 wt.%, each based on the total weight of layer V and / or the molding compound of layer V.

[0088] In a preferred embodiment, a further outer layer (layer VIII), optionally a further outer layer (layer IX), optionally a further outer layer (layer X) and optionally further outer layers are attached to the outside, each comprising independently of one another a molding compound preferably containing polyamides, their copolymers and / or mixtures thereof.

[0089] In a preferred embodiment, the multilayer hollow body is coilable, particularly in industrially relevant diameters, and is preferably a coilable tube.

[0090] In a preferred embodiment, the hollow body has three, four, five, six or seven layers.

[0091] The hollow body according to the invention can be designed in particular in five layers, should additional encapsulation of the barrier layer be necessary. The encapsulation provides protection against leaching and other migration of substances into the surrounding and / or Guided medium understood.

[0092] In a preferred embodiment, the multilayered hollow body - a hollow profile, preferably a pipe or a container; and / or - a component of a fuel-carrying system; and / or - a gas pipeline; and / or - an onshore and / or offshore pipe or at least a section thereof.

[0093] Preferably, the multi-layered hollow body according to the invention is neither a brake line, nor a clutch line, nor a coolant line, nor a cable duct, nor a petrol station supply line, nor a ventilation line, nor an air intake pipe.

[0094] Preferably, the multi-layered hollow body according to the invention is not a component of an automobile.

[0095] In a preferred embodiment, the multilayer hollow body contains layer I and layer II, or does not contain these layers, and layer III is a barrier and inner layer, layer IV is a molding compound comprising or containing PA 6 and PA 6.12, and layer V is a molding compound comprising or containing chain-extended PA 12. No additional outer layers adjoin the outer layers, and layers I, II (if present), III, IV, and V follow directly one another (see Figure 3). This multilayer hollow body is an onshore pipe and is characterized in that it can be welded using conventional methods, in particular by butt welding and / or socket welding.

[0096] In a preferred embodiment, the multilayer hollow body contains layer I and layer II, or does not contain these layers, and layer III is a barrier and inner layer, layer IV is a molding compound comprising or containing PA 6 and PA 6.12, layer V is a molding compound comprising or containing chain-extended PA 12, a second outer layer (layer VI) is a molding compound comprising or containing carbon fiber-reinforced PA 12, a third outer layer (layer VII) is a protective sheath, and layers I, II (if present), III, IV, V, VI, and VII follow directly one another (see Figure 2). This multilayer hollow body is an offshore pipe and is characterized in that it can be welded using conventional methods, in particular by butt welding and / or socket welding.

[0097] The person skilled in the art understands that, provided that the multilayer hollow body according to the invention has a layer VI which comprises a molding compound containing carbon fiber reinforced PA 12 in the form of unidirectionally endless fiber reinforced strips, the resulting hollow bodies can be welded by socket welding, but not by butt welding.

[0098] In a particularly preferred embodiment, the multilayer hollow body is a three- or five-layer chain-extended PA multilayer tube (i.e., a multilayer tube containing chain-extended polyamide) with barrier properties against H2 permeation, or at least a part of this tube, each configured for offshore and / or onshore applications.

[0099] In a particularly preferred embodiment, the multilayer hollow body is an offshore pipe which contains or consists of layers in exactly the composition and arrangement shown in Figure 2.

[0100] In a particularly preferred embodiment, the multilayer hollow body is an onshore pipe which contains or consists of layers in exactly the composition and arrangement shown in Figure 3.

[0101] In a preferred embodiment, the multi-layered hollow body, in particular the offshore pipe and / or onshore pipe, contains a steel content of at most 20 wt.%, at most 10 wt.% or at most 5 wt.%, in each case based on the total weight of the hollow body; preferably the multi-layered hollow body, in particular the offshore pipe and / or onshore pipe, contains no steel.

[0102] In a preferred embodiment, layer I and / or layer II and / or layer III and / or layer IV and / or layer V and / or layer VI and / or layer VII comprise the respective molding compound. The terms "layer" and "molding compound" can then be used synonymously.

[0103] The polyamide molding compounds used according to the invention may contain, in addition to the polymer components described, further additives. These further additives are, taking into account the definitions given below, for example: a) stabilizers, b) additional polymers, c) impact modifiers, d) plasticizers, e) pigments and / or dyes, f) additives that increase electrical conductivity, and g) processing aids.

[0104] Especially preferred are Stabilizers in an amount of up to 2 wt.%, preferably up to 1.5 wt.% and particularly preferably up to 1.2 wt.% for use and / or Pigments in an amount of up to 1.5 wt.%, preferably up to 1.2 wt.% and particularly preferably from 0.1 to 1 wt.% and / or Impact modifiers are used in an amount of up to 10 wt.%, preferably up to 9 wt.% and particularly preferably up to 8 wt.%.

[0105] In a preferred embodiment, the molding compounds contain an effective amount of an oxidation stabilizer, and particularly preferably an effective amount of an oxidation stabilizer in combination with an effective amount of a copper-containing stabilizer. Suitable oxidation stabilizers include, for example, aromatic amines, sterically hindered phenols, phosphites, phosphonites, thiosynergists, hydroxylamines, benzofuranone derivatives, acryloyl-modified phenols, etc. Such oxidation stabilizers are commercially available in a variety of types, for example under the trade names Naugard 445, Irganox 1010, Irganox 1098, Irgafos 168, P-EPQ, or Lowinox DSTDP. In general, the molding compounds contain about 0.01 to about 2 wt%, and preferably about 0.1 to about 1.5 wt%, of an oxidation stabilizer.

[0106] Furthermore, the molding compounds may also contain a UV stabilizer or a HALS-type light stabilizer. Suitable UV stabilizers are primarily organic UV absorbers, such as benzophenone derivatives, benzotriazole derivatives, oxalanilides, or phenyltriazines. HALS-type light stabilizers are tetramethylpiperidine derivatives; these are inhibitors that act as radical scavengers. UV stabilizers and light stabilizers can be advantageously used in combination. Both are commercially available in a wide variety of types; the manufacturer's instructions should be followed regarding dosage.

[0107] The molding compounds may additionally contain a hydrolysis stabilizer such as a monomeric, oligomeric or polymeric carbodiimide or a bisoxazoline.

[0108] Other polymers that may be included as additives in the molding compounds are, for example, polyetheramides or polytetrafluoroethylene (PTFE).

[0109] Impact-enhancing rubbers for polyamide molding compounds are state of the art. They contain functional groups derived from unsaturated functional compounds that are either polymerized into the main chain or grafted onto it. The most common are EPM or EPDM rubbers, which are radically grafted with maleic anhydride. Such rubbers can also be used together with an unfunctionalized polyolefin, such as isotactic polypropylene, as described in EP-A-0 683 210.

[0110] Plasticizers and their use in polyamides are well known to experts. A general overview of plasticizers suitable for polyamides can be found in Gächter / Müller, Kunststoffadditive (Plastic Additives), C. Hanser Verlag, 2nd edition, p. 296.

[0111] Suitable plasticizers include, for example, esters of p-hydroxybenzoic acid with 2 to 20 carbon atoms in the alcohol component or amides of arylsulfonic acids with 2 to 12 carbon atoms in the amine component, preferably amides of benzenesulfonic acid.

[0112] Plasticizers used include ethyl p-hydroxybenzoate, p- Octyl hydroxybenzoate, i-hydroxybenzoate, n-octyl toluenesulfonic acid, n-butyl benzenesulfonic acid or 2-ethylhexyl benzenesulfonic acid are possibilities.

[0113] Suitable pigments and / or dyes include, for example, soot, iron oxide, zinc sulfide, ultramarine, nigrosine, pearlescent pigments and metallic flakes.

[0114] Additives that increase electrical conductivity include, for example, conductive carbon black or carbon nanotubes.

[0115] Suitable processing aids include, for example, paraffins, fatty alcohols, fatty acid amides, stearates such as calcium stearate, paraffin waxes, montanates or polysiloxanes.

[0116] The respective molding compound is produced from the individual components by mixing them in the melt in a manner known to experts.

[0117] The EVOH of the barrier layer (layer III) is a copolymer of ethylene and vinyl alcohol. The ethylene content in the copolymer is typically 24 to 44 mol%, preferably 27 to 38 mol%, and particularly preferably 30 to 35 mol%. A variety of types are commercially available. In addition to the EVOH, the molding compound may contain other additives, as is common in barrier layer applications, according to the prior art. Such additives are generally the know-how of the EVOH supplier.

[0118] In a preferred embodiment, only the barrier layer (layer III) contains EVOH.

[0119] In a preferred embodiment, only the barrier layer (layer III) contains and consists of EVOH (100 wt.%).

[0120] EVOH barrier layers are known to experts from publication EP 1 216 826 B1.

[0121] When using the multilayer hollow body according to the invention for conveying or storing flammable liquids, gases, or dusts, such as fuel or fuel vapors, it is recommended to make at least one of the layers belonging to the composite electrically conductive. This can be achieved by compounding with an electrically conductive additive using any prior art method. Examples of conductive additives that can be used include conductive carbon black, metal flakes, metal powder, metallized glass beads, metallized glass fibers, metal fibers (e.g., made of stainless steel), metallized whiskers, carbon fibers (also metallized), intrinsically conductive polymers, or graphite fibrils. Mixtures of different conductive additives can also be used.

[0122] In the preferred case, the electrically conductive layer is in direct contact with the medium to be conveyed or stored and has a specific surface resistance of at most 10 9 Q / square and preferably a maximum of 10 6 Q / square. The measurement method for determining the resistance of multilayer tubes is described in SAE J 2260 from November 2004. In this case, either the entire layer is electrically conductive, or it consists of two sublayers, one of which is electrically conductive and the other not. Preferably, the electrically conductive innermost layer is layer 1.

[0123] When the multilayer hollow body according to the invention is implemented as a hollow profile (e.g., a tube) or container, it can be further encased with an additional elastomer layer. Both crosslinking rubber compounds and thermoplastic elastomers are suitable for this encasement. The encasement can be applied to the multilayer hollow body or parts with or without the use of an additional adhesion promoter, for example, by coextrusion, extrusion via a transverse die, or by sliding a pre-fabricated elastomer tube over the finished extruded multilayer tube. The encasement typically has a thickness of 0.1 to 4 mm, and preferably 0.2 to 3 mm.

[0124] Suitable elastomers include, for example, chloroprene rubber, ethylene / propylene rubber (EPM), ethylene / propylene / diene rubber (EPDM), epichlorohydrin rubber (ECO), chlorinated polyethylene, acrylate rubber, chlorosulfonated polyethylene, silicone rubber, plasticized PVC, polyetheresteramides or polyetheramides.

[0125] The multilayer hollow body can be manufactured in one or more stages, for example, by means of single-stage processes such as multi-component injection molding, co-extrusion, co-extrusion blow molding (e.g., also 3D blow molding, tube extrusion into an open mold half, 3D tube manipulation, suction blow molding, 3D suction blow molding, sequential blow molding) or by means of multi-stage processes, as described, for example, in US 5,554,425. If the multilayer hollow body according to the invention has a layer VI comprising a molding compound containing carbon fiber-reinforced PA 12, in particular in the form of unidirectionally continuous fiber-reinforced strips, then winding and subsequent extrusion take place after the initial extrusion.

[0126] In a second aspect, the invention relates to the use of the multilayer hollow body according to the invention. - as a hollow profile, preferably as a pipe or as a container; and / or - as a component of a fuel-carrying system; and / or - as a gas pipeline; and / or - as an onshore and / or offshore pipe or at least as a part thereof.

[0127] Preferably, the multi-layered hollow body according to the invention is not used as a brake line, as a clutch line, as a coolant line, as a cable duct, as a filling station supply line, as a ventilation line and / or as an air intake pipe.

[0128] Preferably, the multi-layered hollow body according to the invention is not used in an automobile.

[0129] In a third aspect, the invention relates to a fuel-carrying device comprising the multi-layered hollow body according to the invention.

[0130] The fuel-carrying device is preferably a fuel line, a fuel tank, a hydraulic line, a brake line, a clutch line, a coolant line, a liner for rigid or flexible pipes in the oil or gas production industry, or a line of an umbilical.

[0131] In a fourth aspect, the invention relates to a fuel-carrying system comprising the multi-layered hollow body and / or the device according to the invention.

[0132] The fuel-carrying system is preferably - an onshore pipeline, an offshore pipeline or a combination thereof.

[0133] Another example of a plant according to the invention is a floating wind farm, which preferably generates H2 directly on a platform and exports it to land.

[0134] The fuel is preferably hydrogen (H2), H2S, CO2, CH4 or a mixture thereof, particularly preferably hydrogen (H2).

[0135] All definitions of the multilayer hollow body according to the first aspect of the invention are also applicable in connection with the second, third and fourth aspects of the invention.

[0136] The invention will be explained by way of example in the following experimental section.

[0137] Figure 1 illustrates that H2 permeation in the PA 12-EVOH-MLT system according to the invention is drastically reduced compared to monotubes of the same thickness made of other polymers or polymer systems. The gas permeability G is plotted on the y-axis.

[0138] H₂ permeation was determined as follows: The tubes were sealed at one end with a blind flange equipped with measuring ports for continuous pressure and temperature monitoring. After sealing, the test tubes were filled with the test gas and stored for conditioning for 4–6 weeks. During conditioning, the tube is kept in contact with the test gas until the plastic is completely saturated. and a constant permeation rate was established. After completion of the conditioning phase, the pipes were clamped into special permeation measuring cells and prepared for the test. The measuring cells are gas-tight stainless steel chambers that enclose the pipe over a test length of approximately 30 cm. The measuring cells themselves are equipped with two measuring ports for pressure and temperature monitoring and one port for sampling. At the beginning of the measurement, the measuring cells were purged with nitrogen and set to an overpressure of approximately 100 mbar. The permeate that penetrates the pipe wall over the test length is collected in the measuring cell. During the test period, the hydrogen permeate concentrates in the measuring cell. Gas samples were taken from the measuring cells at regular intervals and analyzed by gas chromatography in the testing laboratory.The gas composition (N₂, H₂) indicates the amount of hydrogen that has permeated the pipe wall per unit of time. The increase in hydrogen concentration in the measuring cell follows a linear function and reflects the permeation rate. The permeation rate is determined with sufficient accuracy using at least four measurement points (pressure and temperature constant). Taking into account the inner surface area (permeation area) and the partial pressures (absolute), the gas permeability G is calculated from the permeation rate, and the permeation coefficient (PC) is calculated using the pipe wall thickness. In tests at room temperature (approx. 20°C), the permeation coefficients of hydrogen were determined at various internal pressures, with the plastic pipes supported only by the seals at the ends of the permeation cell (no support for the pipe surfaces).

[0139] By incorporating an EVOH barrier layer, the permeation coefficient (PC) can be reduced by up to three orders of magnitude in the temperature range relevant for Hz applications (30 °C - 50 °C).

[0140] Figure 2 shows an offshore pipe. From the inside out, it consists of the following layers: - Layer I: possibly high-purity (HP = high purity) inner layer, - Layer II: possibly additional adhesion promoter (specific for HP inner layer), - Layer III: H2 barrier (EVOH) as inner layer, - Layer IV: Detention mediators, - Layer V: chain-extended structural tube, - Layer VI: pressure-bearing continuous reinforcement, and - Layer VII: Protective tube. Layers III to V form the MSR as a liner (MSR = multilayer pipe system). Layers I to V form the HP-MSR as a liner (HP = high purity; MSR = multilayer pipe system).

[0141] Figure 3 shows an onshore pipe. From the inside out, it consists of the following layers: - Layer I: possibly high-purity (HP = high purity) inner layer, - Layer II: possibly additional adhesion promoter (specific for HP inner layer), - Layer III: H2 barrier (EVOH) as inner layer, - Layer IV: Detention mediators, and - Layer V: chain-extended structural tube. Layers III to V form the MSR as a pressure pipe (MSR = multilayer pipe system). Layers I to V form the HP-MSR as a pressure pipe (HP = high purity; MSR = multilayer pipe system).

[0142] Figures 4 and 5 relate to mirror welding of onshore pipes according to Figure 3.

[0143] Figure 4 shows that in an intact welded test specimen, no EVOH ingress into the weld seam is visually detectable, i.e., the welding process does not cause any mechanical weakening of the weld seam.

[0144] Figure 5 shows the relative change in the properties "tensile stress", "elongation at yield", and "modulus" of welded monotubes (white) and MLTs (gray), i.e., multilayer pipe systems according to the invention, compared to non-welded PA 12 monotubes (0% reference). According to the invention, no EVOH ingress occurs in the weld seam. Therefore, there is no significant impact on the structural integrity of the weld seam; the impact is only within the range of the usual standard deviation.

[0145] As shown in Figure 6, FEM simulations were performed to calculate the minimum bending radius (MBR) at 23 °C and an innermost EVOH barrier layer:

[0146] It should be noted that the failure criterion for the MBR is buckling of the pipe. Therefore, a higher SDR value / smaller wall thickness leads to earlier buckling. The high stiffness of EVOH (3800 MPa) combined with relatively low yield strength (35 MPa) results in a higher risk of buckling compared to PA 12 (1320 MPa and 40 MPa). For a 110 SDR17 pipe, the MBR would be 1.85 m, which is significantly larger compared to a single-layer pipe of the same dimensions, which would have an MBR of 1.3 m.

Claims

1 . A multi-layer hollow body for the transport, transmission, distribution and / or storage of gases and / or liquids, which has or consists of the following layers from the inside to the outside: - optionally a layer I comprising a molding compound containing polyethylene (PE), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), poly(tetrafluoroethylene-perfluoromethyl vinyl ether) (MFA), fluoroethylene-propylene (FEP) and / or ethylene-chlorotrifluoroethylene (ECTFE); and preferably comprising or consisting of PE-HP, PVDF-HP, PFA-HP, MFA-HP and / or FEP-HP; - optionally a layer II, which is an adhesion promoter layer and comprises or consists of a molding compound containing PA 6, PA 6.12, their copolymers and / or mixtures thereof; - a barrier layer (layer III) which comprises or consists of a molding compound containing ethylene-vinyl alcohol copolymer (EVOH); - an adhesion promoter layer (layer IV) which comprises or consists of a molding compound containing PA 6, PA 6.12, their copolymers and / or mixtures thereof; - a layer V, which comprises a molding compound containing at least one chain-extended polyamide; and preferably comprises chain-extended PA 12, chain-extended PA 6.12, chain-extended bio-PA, their copolymers and / or mixtures thereof; and particularly preferably comprises or consists of chain-extended PA 12, wherein the chain-extended polyamides are obtainable with the aid of a chain-extending additive having at least 2 carbonate units per molecule; - optionally a layer VI which comprises or consists of a molding compound containing carbon fiber reinforced PA 12; and - if necessary, a layer VII, which is a protective coating.

2. The multilayer hollow body according to claim 1, characterized in that - the molding compound of layer V is obtainable by condensing a PA 12, PA 6.12 and / or Bio-PA molding compound with a compound having at least two carbonate units and the polyamide portion of the PA 12, PA 6.12 and / or Bio-PA molding compound contains, due to the manufacturing process, at least 5 ppm of phosphorus in the form of an acidic compound, where a) 0.001 to 10% by weight, based on the polyamide, of a salt of a weak acid is added to the polyamide before compounding or during compounding, and b) a mixture of the finished compound and 0.005 to 10% by weight, based on the polyamide, of the compound having at least two carbonate units is prepared.

3. The multilayer hollow body according to claim 2, characterized in that - the polyamide component contains 20 to 500 ppm of phosphorus in the form of an acidic compound; and / or - 0.001 to 5 wt.%, preferably 0.01 to 2.5 wt.%, particularly preferably 0.05 to 1 wt.%, of a salt of a weak acid is added to the polyamide, and the weak acid preferably has a pKa value of 2.5 or higher and / or the salt of the weak acid is preferably an alkali metal salt, an alkaline earth metal salt, the salt of a metal of main group III, the salt of a metal of transition group II, or an ammonium salt; and / or - the polyamide was produced using a diamine or polyamine as a regulator; and / or - the compound with at least two carbonate units is used as a masterbatch.

4. The multi-layer hollow body according to one or more of the preceding claims, characterized in that this - does not contain layer I; or - does not contain layer I and layer II and layer III is the barrier and inner layer.

5. The multi-layer hollow body according to one or more of the preceding claims, characterized in that - layers I, II, III, IV and V, or - layers I, II, III, IV, V, VI and VII, or - layers III, IV and V, or layers III, IV, V, VI and VII follow one another directly; and / or Layer III is arranged off-center; and / or - the thickness of layer III is at least 0.2 mm and at most 0.6 mm, the thickness of layer IV is at least 0.1 mm and at most 0.2 mm, and the thickness of layer V is at least 6.0 mm and at most 10.0 mm, each preferably determined in accordance with the standard DIN EN 13480-3:2017-12; and / or - the internal diameter of the multi-layer hollow body according to the invention, in particular of the onshore and / or offshore pipe, is at least 30 mm or at least 50 mm and / or at most 160 mm or at most 300 mm or at most 350 mm.

6. The multi-layer hollow body according to one or more of the preceding claims, characterized in that the molding compound of layer V - additional polyamides, their copolymers and / or mixtures thereof, - vorzugsweise PA 8, PA 9, PA 10, PA 11, PA 12, PA 4.6, PA 6.10, PA 6.12, PA 6.13, PA 6.14, PA 6.16, PA 8.10, PA 8.13, PA 9.10, PA 9.12, PA 10.10, PA 10.12, PA 10.14, PA 10.16, PA 10.18, PA 12.12, PA DACH.6 (Diaminocyclohexan), PA DACH.10, PA DACH.12, PA DACH.10 / 11, PA PACM.6 (4,4-Diaminodicyclohexylmethan), PA PACM.10, PA PACM.12, PA MACM.6 (3,3'-Dimethyl-4,4'-diaminocyclohexylmethan), PA MACM.10, PA MACM.12,. PA 6.T (T = Terephthalsäure), PA 9.T, PA 10.T, PA 12.T, PA 6.I (I = Isophthalsäure), PA 9.I, PA 10.1, PA 12.1, PA 6.N (2,6-Naphthalindicarbonsäure), PA 10.N, PA 12.N, PA MXD.6 (MXD = meta- ,6-Diamino-2,2,4-trimethylhexan), PA ND.10, PA ND.12, deren Copolymeren und / oder Mischungen davon.

7. The multi-layer hollow body according to one or more of the preceding claims, characterized in that - the molding compound of layer I contains PE-HP, PVDF-HP, PFA-HP, MFA-HP and / or FEP-HP, each individually or in total in an amount of at least 50 wt.%, preferably at least 80 wt.%, particularly preferably at least 85 wt.% and especially preferably at least 90 wt.%, in each case based on the total weight of layer I and / or the molding compound of layer I; and / or in the molding compound of layer III, the EVOH has an ethylene content of at least 10 wt.%, more preferably 20 to 50 wt.%, more preferably 24 to 44 wt.%, more preferably 27 to 38 wt.%, more preferably 30 to 35 wt.%; and / or - the molding compound of layer V contains chain-extended PA 12, chain-extended PA 6.12, chain-extended bio-PA, their copolymers and / or mixtures thereof, in each case individually or in total in an amount of at least 80% by weight, preferably at least 85% by weight and particularly preferably at least 90% by weight, in each case based on the total weight of layer V and / or the molding compound of layer V.

8. The multi-layer hollow body according to one or more of the preceding claims, characterized in that it is produced by a single- or multi-stage extrusion process or co-extrusion process, optionally in combination with a winding.

9. The multi-layer hollow body according to one or more of the preceding claims, characterized in that it is windable, in particular windable in industry-relevant diameters, and is preferably a windable tube.

10. The multi-layer hollow body according to one or more of the preceding claims, characterized in that (i) it contains or does not contain layer I and layer II and layer III is the barrier and inner layer, Layer IV is a molding compound which comprises or includes PA 6 and PA 6.12, Layer V is a molding compound which comprises or contains chain-extended PA 12, no additional outer layers are connected to the outside, layers I, II, if present, III, IV and V follow one another directly, and the multi-layer hollow body is preferably weldable, particularly preferably mirror-weldable and / or socket-weldable; or (ii) it contains or does not contain layer I and layer II and layer III is the barrier and inner layer, Layer IV is a molding compound which comprises or includes PA 6 and PA 6.12, Layer V is a molding compound which comprises or contains chain-extended PA 12, a further outer layer (layer VI) is connected to the outside, which is a molding compound which comprises or contains carbon fiber-reinforced PA 12, a further outer layer (layer VII) is connected to the outside, which is a protective coating, layers I, II, if present, III, IV, V, VI and VII follow one another directly, and the multi-layer hollow body is preferably weldable, particularly preferably mirror-weldable and / or socket-weldable. 11 . The multi-layer hollow body according to one or more of the preceding claims, characterized in that it - is a hollow profile, preferably a pipe or a container; and / or - is a component of a fuel-carrying system; and / or - is a gas pipe; and / or - is an onshore and / or offshore pipe or at least a section thereof.

12. The multi-layer hollow body according to one or more of the preceding claims, characterized in that - the molding compound of layer I and / or the molding compound of layer II and / or the molding compound of layer III and / or the molding compound of layer IV and / or the molding compound of layer V and / or the molding compound of layer VI and / or the molding compound of layer VII contains one or more additives, preferably selected from the group consisting of stabilizers, additional polymers, impact modifiers, plasticizers, pigments and / or dyes, additives that increase electrical conductivity, processing aids and combinations thereof and / or preferably in an amount of at most 50 wt.%, preferably at most 40 wt.%, particularly preferably at most 35 wt.% and especially preferably at most 30 wt.%, in each case based on the total weight of the respective layer and / or molding compound; and / or - it contains one or more additional layers selected from an electrically conductive layer and an elastomer coating.

13. The multi-layer hollow body according to one or more of the preceding claims, characterized in that the molding compound of layer I and / or the molding compound of layer II and / or the molding compound of layer III and / or the molding compound of layer IV and / or the molding compound of layer V and / or the molding compound of layer VI and / or the molding compound of layer VII, each independently of one another, contains no plasticizer.

14. Use of the multilayer hollow body according to one or more of the preceding claims - as a hollow profile, preferably as a pipe or as a container; and / or - as a component of a fuel-carrying system; and / or - as a gas pipe; and / or - as an onshore and / or offshore pipe or at least as a section thereof.

15. A fuel-carrying installation, in particular an onshore pipeline, an offshore pipeline or combinations thereof, comprising the multi-layer hollow body according to one or more of claims 1 to 13.

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