EP4003721A1

EP4003721A1 - Multilayer structure for transporting or storing hydrogen

Info

Publication number: EP4003721A1
Application number: EP20757388.2A
Authority: EP
Inventors: Gilles Hochstetter; Patrick Dang; Thibaut SAVART
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2019-07-30
Filing date: 2020-07-28
Publication date: 2022-06-01
Also published as: WO2021019181A1; KR20220040485A; JP2022542263A; FR3099409A1; FR3099409B1; US20220258446A1; CN114174066A

Abstract

The present invention relates to a multilayer structure selected from a reservoir, a pipe or a tube, for transporting, distributing or storing hydrogen, comprising, from the inside to the outside, at least one sealing layer and at least one composite reinforcing layer, said innermost composite reinforcing layer being welded to said outermost adjacent sealing layer, said sealing layers consisting of a composition predominantly comprising at least one semi-crystalline thermoplastic polymer P1i (i = 1 to n, n being the number of sealing layers), the Tf of which, as measured according to ISO 11357-3: 2013, is less than 280 °C, in particular less than 265 °C, wherein the at least one thermoplastic polymer of each sealing layer may be the same or different, and at least one of said composite reinforcing layers consisting of a fibrous material in the form of continuous fibers impregnated with a composition predominantly comprising at least one thermoplastic polymer P2j, (j = 1 to m, m being the number of reinforcing layers), which is in particular semi-crystalline, said thermoplastic polymer P2j having a Tg, as measured according to ISO 11357-3: 2013, greater than the maximum temperature of use of said structure (Tu), with Tg ≥ Tu + 20 °C, Tu being greater than 50 °C, in particular greater than 100 °C.

Description

DESCRIPTION

TITLE: MULTI-LAYER STRUCTURE FOR THE TRANSPORT OR STORAGE OF

HYDROGEN

[Technical area]

The present patent application relates to composite multilayer structures for the transport, distribution or storage of hydrogen and their manufacturing process. [Prior art]

One of the goals sought in the automotive field is to offer vehicles that pollute less and less. Thus, electric or hybrid vehicles comprising a battery aim to gradually replace thermal vehicles, such as gasoline or diesel vehicles. However, it turns out that the battery is a relatively complex component of the vehicle. Depending on the location of the battery in the vehicle, it may be necessary to protect it from impact and the external environment, which can be extreme temperatures and varying humidity. It is also necessary to avoid any risk of flames.

In addition, it is important that its operating temperature does not exceed 55 ° C so as not to damage the battery cells and preserve its life. Conversely, for example in winter, it may be necessary to raise the temperature of the battery in order to optimize its operation.

In addition, the electric vehicle still suffers today from several problems, namely the autonomy of the battery, the use in these rare earth batteries whose resources are not inexhaustible as well as a problem of electricity production in different countries to be able to recharge the batteries.

Hydrogen therefore represents an alternative to the electric battery since hydrogen can be transformed into electricity by means of a fuel cell and thus power electric vehicles.

However, the storage of hydrogen is technically difficult and expensive because of its very low molar mass and its very low liquefaction temperature, all

especially when it comes to mobile storage. However, to be efficient, storage must be carried out in a low volume, which means that the hydrogen must be kept under high pressure, given the vehicle operating temperatures. This is the case, in particular, with fuel cell hybrid road vehicles for which the aim is a range of around 600 to 700 km, or even less for mainly urban uses in addition to an electric base on batteries.

Hydrogen tanks generally consist of a metallic liner which must prevent the permeation of hydrogen. This first envelope must itself be protected by a second envelope (in composite materials in general) intended to withstand the internal pressure of the tank (for example, 700 bars) and resistant to possible shocks or heat sources. The valve system must also be safe.

According to the Memento sur l'hydrogen from the French association for hydrogen and the fuel cell (AFHYPAC) Sheet 4.2, revision December 2016, the storage and distribution of hydrogen under pressure is a standard practice, for many years, with cylinders or assemblies of cylindrical cylinders, in steel, inflated to 20 or 25 MPa (types I and II). The downside of this storage method is

the bulk - only 14 kg / m3 at 20 MPa and at ordinary temperature (21 ° C) against 100 kg / m ³ for methane - and above all the weight resulting from the use of steels with low stress levels for avoid hydrogen embrittlement problems. The situation has radically changed with the emergence of so-called type III or IV composite tank technology. Their basic principle is to separate the two essential functions of sealing and mechanical strength in order to manage them one

independently of the other. In this type of tank, a resin bladder (thermosetting or thermoplastic), also called a liner (or sealing sheath), is associated with a reinforcing structure made up of fibers (glass, aramid, carbon) also called sheath or reinforcing layer which allow to work at much higher pressures while reducing the mass and avoiding the risk of explosive rupture in the event of severe external attacks. This is how 70 MPa (700bars) practically became the current standard.

In type IV tanks, the liner and the backing layer are made of different materials, which has the disadvantage of exhibiting a lack of adhesion between the liner and the backing layer, which poses problems of liner collapse. when simultaneously, there is on the one hand an accumulation of gas at the interface between the liner and the composite and, on the other hand, a drop in the internal pressure of the reservoir.

This problem has given rise to the development of type V reservoirs, which are based on using the same polymer for the liner and for the matrix of the composite in order to ensure excellent and lasting adhesion between the liner and the composite.

In the case of the transport or distribution of hydrogen by means of rigid or flexible pipes, it is also preferable for the hydrogen to be in a low volume and therefore under high pressure, to ensure a sufficient flow rate. Thus, as for the storage, transport or distribution of hydrogen, it is interesting to use composite pipes (pipes) composed of a sealing sheath (ensuring tightness and chemical resistance), reinforced by an outer layer made of a composite material, which is produced by filament winding, from unidirectional tapes (UD) deposited in successive layers on the liner. When you want to make this hose flexible, it is It is interesting to wind the UD tapes with one or more angles of orientation with respect to the axis of the pipe so that the composite reinforcement can withstand the deformations of the composite pipe during its use. The composite reinforcement allows the pipe to resist the internal pressure of the pipe generated by the transported fluid.

As with storage tanks, the sealing sheath must resist collapse, especially during production shutdowns resulting in a sudden drop in pressure. This risk of collapse exists when the sheath is not adherent to the composite reinforcement and then gas may be present between the sealing sheath and the composite reinforcement. To avoid this phenomenon, one solution is to put an internal reinforcement in the pressure sheath called a carcass: this reinforcement, often metallic, is perforated to be flexible and is therefore not waterproof to the fluid transported. It adds weight, a degree of complexity and an extra cost to the hose. Also, to reduce the weight, or even eliminate the internal carcass of composite pipes, it is necessary for the composite reinforcement to adhere to the sealing sheath, as in the case of type V storage tanks.

Furthermore, the sealing sheath must be able to be extruded continuously, possibly on the support of an internal carcass, as indicated above. This sealing sheath must be sufficiently chemically stable so that its mechanical characteristics and its tightness do not deteriorate in a crippling manner during the life of the tank or hose.

In the case of a flexible pipe comprising an internal metal casing, the sealing sheath must also withstand the effect of the flow of the material constituting it, following the stresses generated on the sealing sheath by the internal pressure of the pipe. Creep occurs in the joints (space or clearance) between the metal armors (for example of self-stapled zeta geometry or T) on which the sheath rests when the pipe is pressurized by the effluent transported, creating growths of material which generate stress concentrations and are therefore privileged rupture zones of the sealing sheath: the material constituting the sealing sheath must therefore also withstand these stress concentrations.

For example, Airborne has developed various flexible hoses, without internal carcass and comprising a sealing sheath adhering to the composite reinforcement, comprising:

a PA 11 liner with a PA11 FC composite (JIP completed in 2011) or a PA12 liner with PA12 FC composite or a PVDF liner with a PVDF FC composite. However, all these structures have the drawback that the matrix of the composite reinforcement has a glass transition temperature, Tg, lower than the temperature of use of the pipe, Tu, ie, in the case of pipes based on PA1 1 or PA12 , a Tg of 50 ° C in the dry state for a pipe use temperature, Tu, of 60 to 80 ° C and in the case of PVDF, a Tg of -40 ° C, for a continuous use temperature above 100 ° C and often close to 130 ° C. In the particular case of PVDF, the rigidity (modulus) of the matrix remains high beyond its Tg until another transition is reached, the alpha transition towards 100 ° C, beyond its behavior becomes purely rubbery. Thus, in all the industrial and commercial cases of composite pipe with a TP matrix that we have just mentioned, the matrix of the composite reinforcement is in a completely rubbery state, at the temperature Tu of use of the composite pipe.

To remedy this problem and have a composite reinforcement whose matrix has a Tg greater than the maximum temperature of use, so as not to be in a rubbery state at the temperature of use, in this case 130 ° C, Kutting & Total then Vitrex and Magma, have developed a solution composed of a PEEK liner reinforced with a PEEK matrix composite, too. The Tg of PEEK is 140 ° C and therefore meets the requirement for high rigidity thanks to the fact that this Tg is greater than the maximum temperature of use. The disadvantage is that, as a consequence, the sealing sheath (liner) is also very rigid, which can limit its resistance to fatigue and which is a major drawback for the production of flexible pipes. In addition, the temperature for using this type of sealing sheath is very high (typically 380-400 ° C) and in the case of the usual transformation process which is the extrusion of tubes, this poses great difficulties. in terms of tools and process control.

In addition, Ticona (Celanese) in partnership with Airborne, offers a composite pipe comprising a PPS FC reinforcement and a PPS sealing sheath.

For Tu> 90 ° C, this structure poses the same problem for the matrix of the composite as the solution based on PVDF (that is to say Tg <Tu), but which also presents the problem of the temperature of transformation (typically 350 ° C versus 250 ° C, for PPS and PVDF, respectively).

For Tu <90 ° C, PPS is suitable for the matrix of the composite but the problem of the extrusion temperature of the sealing sheath (liner) remains, as well as that of its great rigidity, which limits the flexibility of the liner. composite pipe.

The case of hydrogen tanks poses a similar technical problem because its rapid filling with hydrogen causes an increase in the temperature of the tank due to the compression of the hydrogen, in particular at around 1 10 ° C, which requires oversizing of the composite, in the case where the matrix of the composite has a Tg below this temperature.

Thus, it remains to optimize on the one hand, the matrix of the composite so as to optimize its mechanical resistance at high temperature and on the other hand the material composing the sheath. sealing, so as to optimize its processing temperature, without degrading the adhesion of the composite reinforcement to the sealing sheath. Thus, the possible modification of the composition of the material making up the sealing sheath, which will be made to ensure miscibility or less partial with the matrix of the composite, must not result in a significant increase in the manufacturing temperature (extrusion). blowing, injection, rotational molding ...) of this liner, compared to what is practiced today with polyamides and PVDFs.

These problems are solved by providing a multilayer structure of the present invention which is a fully bonded, "bi-material" composite pipe or tank, and composed of a high strength composite reinforcement, that is. that is to say comprising a high Tg matrix, deposited in particular by filament winding on a liner previously extruded at relatively low temperature. The adhesion between the composite and the liner is very good.

Throughout this description, the terms "liner", "sealing sheath" and "pressure sheath" have the same meaning.

The present invention therefore relates to a multilayer structure chosen from a tank, a pipe or tube, intended for transporting or storing hydrogen, comprising, from the inside to the outside, at least one sealing layer and at least one. composite reinforcement layer,

said innermost composite reinforcing layer being welded to said outermost adjacent waterproofing layer,

said sealing layers consisting of a composition mainly comprising at least one thermoplastic polymer P1 i (i = 1 to n, n being the number of sealing layers) semi-crystalline whose Tf, as measured according to ISO 11357 -3: 2013, is below 280 ° C, especially below 265 ° C,

said at least one thermoplastic polymer of each sealing layer possibly being the same or different, and at least one of said composite reinforcing layers consisting of a fibrous material in the form of continuous fibers impregnated with a composition mainly comprising at least a thermoplastic polymer P2j, (j = 1 to m, m being the number of reinforcement layers) in particular semi-crystalline, said thermoplastic polymer P2j having a Tg, as measured according to ISO 1 1357-3: 2013, greater than the maximum temperature of use of said structure (Tu), with Tg> Tu + 20 ° C, in particular Tg> Tu + 30 ° C, Tu being greater than 50 ° C, in particular greater than 100 ° C.

The inventors have therefore unexpectedly found that the use of a different polymer for the matrix of the composite and the liner and in particular: a matrix of the composite reinforcement composed of a polymer having a Tg

significantly higher than the maximum temperature of use of the tank or the pipe, Tu, (Tg> Tu + 20 ° C, in particular Tg> Tu + 30 ° C, typically) so as to remain in its vitreous domain and have great rigidity , thus allowing the composite to have high mechanical resistance,

the semi-crystalline polymer composing the liner exhibiting a low melting point, Tm, allowing transformation by extrusion, extrusion blow molding, rotomoulding, injection or by winding a film of pure resin, as the case may be, at a moderate temperature customary for the liner A person skilled in the art, in relation to the Tm of this polymer which is less than 280 ° C, preferably less than 265 ° C. The low Tm semi-crystalline polymers known to date also exhibit a low Tg, which will, in most cases, be below the maximum temperature of use. Consequently, the polymer composing the liner will work in its rubbery domain and will therefore be very flexible and therefore very resistant to fatigue. Its semi-crystalline character will give it good resistance to chemical attack and abrasion and creep,

and, the two aforementioned polymers (that making up the matrix of the composite and that making up the liner) are sufficiently miscible with one another to ensure the weldability of the composite on the liner and therefore excellent adhesion between the liner and the composite. The durability of the adhesion will be guaranteed by the durability of the material constituting the mixture at the interface of the two materials, in other words in the welded joint. The miscibility of the two polymers is reflected, preferably by a single Tg, or failing this, by a signature characteristic of a partially homogeneous mixture, for example by the presence of two Tg values intermediate to the Tg of the two pure polymers.

An immiscibility of two polymers results in the presence of two Tg in the mixture of the two polymers which correspond to the respective Tg of the pure polymers taken separately.

By "multilayer structure" is meant for example a tank, a pipe or tube, comprising or consisting of several layers, in particular two layers.

The waterproofing layer or layers are the innermost layers compared to the composite reinforcing layers which are the outermost layers.

The sealing layer is in contact with the hydrogen even if an inner and therefore the innermost, non-sealed metallic layer, formed by a profiled metal strip wound in a helix such as a strip stapled to form said carcass, is present and on which the sealing layer or layers are coated by extrusion.

When several sealing layers are present, only the innermost layer of the sealing layers is in direct contact with the hydrogen. When only a waterproofing layer and a composite reinforcing layer are present, thus leading to a multilayer structure with two layers, then these two layers are welded and therefore adhere to each other, in direct contact with each other. the other. When several waterproofing layers are present and / or several composite reinforcing layers, then the outermost layer of said waterproofing layers, and therefore opposite the layer in contact with hydrogen, is welded to the layer the innermost of said composite reinforcement, and therefore adhere to one another, in direct contact with one another.

The other composite reinforcement layers are also welded together.

The other waterproofing layers are also welded together.

Regarding the sealing layer (s) and the thermoplastic polymer P1 i One or more sealing layers may or may be present.

Each of said layers consists of a composition mainly comprising at least one thermoplastic PU polymer, i corresponding to the number of layers present i is from 1 to 10, in particular from 1 to 5, in particular from 1 to 3, preferably i = 1 .

The term “predominantly” means that said at least one polymer is present in more than 50% by weight relative to the total weight of the composition.

Advantageously, said at least one majority polymer is present at more than 60% by weight, in particular at more than 70% by weight, particularly at more than 80% by weight, more particularly greater than or equal to 90% by weight 90% by weight, relative to the total weight of the composition.

Said composition can also comprise impact modifiers and / or additives.

The additives can be selected from an antioxidant, a heat stabilizer, a UV absorber, a light stabilizer, a lubricant, an inorganic filler, a flame retardant, a nucleating agent, a plasticizer, a colorant, black carbon and carbon nanofillers.

Advantageously, said composition consists of said thermoplastic polymer P1 i predominantly, from 0 to 5% by weight of impact modifier, from 0 to 5% by weight of additives, the sum of the constituents of the composition being equal to 100% (based on a max of P2i of 90%.

Said at least one majority polymer of each layer may be identical or different. In one embodiment, a single majority polymer is present at least in the sealing layer welded to the composite reinforcing layer.

Thermoplastic polymer P1 i

The term thermoplastic, or thermoplastic polymer, is understood to mean a material which is generally solid at room temperature semi-crystalline, and which softens during an increase. temperature, in particular after passing through its glass transition temperature (Tg), and which may present a clear melting when passing its so-called melting temperature (Tf), and which becomes solid again when the temperature drops below its crystallization temperature.

Tg, Te 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 thermoplastic polymer is preferably in a range of 10,000 to 40,000, preferably 12,000 to 30,000. These Mn values may correspond to inherent viscosities greater than or equal to 0.8 as determined in the m-cresol according to ISO 307: 2007 but by changing the solvent (use of m-cresol instead of sulfuric acid and the temperature being 20 ° C).

As examples of semi-crystalline thermoplastic polymers suitable in the present invention, there may be mentioned:

polyamides, including copolymers, for example polyamide-polyethers, polyesters, and PVDF copolymers and a PVDF / PEI mixture in which PVDF is predominant.

More particularly preferred among the semi-crystalline polymers are the polyamides and their semi-crystalline copolymers.

The nomenclature used to define polyamides is described in standard ISO 1874-1: 201 1 "Plastics - Polyamide materials (PA) for molding and extrusion - Part 1: Description", in particular on page 3 (tables 1 and 2) and is well known to those skilled in the art.

The polyamide can be a homopolyamide or a copolyamide or a mixture thereof. Advantageously, said thermoplastic polymer is a long-chain aliphatic polyamide, that is to say a polyamide having an average number of carbon atoms per nitrogen atom greater than 8.5, preferably greater than 9.

In particular, the long-chain aliphatic polyamide is chosen from:

polyamide 11 (PA11), polyamide 12 (PA12), polyamide 1010 (PA1010), polyamide 1012 (PA1012), polyamide 1212 (PA1012), or a mixture thereof or a copolyamide thereof , in particular PA11 and PA12.

Advantageously, said thermoplastic polymer is a long-chain semi-aromatic polyamide, that is to say a polyamide having an average number of carbon atoms per nitrogen atom greater than 8.5, preferably greater than 9 and a

melting temperature from 240 ° C to less than 280 ° C.

In particular, the long-chain semi-aromatic polyamide is chosen from polyamide 1 1 / 5T or 11 / 6T or 1 1 / 10T. Obviously in this case, the rate of 1 1 must be chosen so that the Tm of said polymers is less than 280 ° C, preferably less than 265 ° C.

Advantageously, each waterproofing layer consists of a composition comprising the same type of polymer, in particular a polyamide.

Advantageously, said composition comprising said polymer P1 i is black in color and capable of absorbing radiation suitable for welding.

There are various methods for soldering polymer elements

thermoplastic. Thus, it can be used heated blades with or without contact, ultrasound, infrared, application of vibrations, a rotation of one element to be welded against the other or even laser welding.

The welding of thermoplastic polymer elements, in particular by laser welding requires that the two elements to be welded have different properties with respect to radiation, in particular laser: one of the elements must be transparent to the

radiation, including laser, and the other must absorb radiation including laser. The radiation, particularly laser, thus passes through the transparent element and then reaches the absorbent element, where it is converted into heat. This makes it possible to melt the contact zone between the two elements and therefore to perform the weld.

In some applications, it is desirable that the two parts to be welded are black in color, therefore including the part transparent to laser radiation.

In order to make them absorbent, it is known practice to add various additives to them, including for example carbon black, which gives the polymer a black color and makes it possible to absorb radiation suitable for welding.

In one embodiment, the welding is carried out by a system chosen from among the laser, infrared heating (IR), heating by led, heating by induction or by weight or high frequency (HF) heating.

In the case where the welding is carried out by laser welding, then the composition P1 i comprises non-agglomerated or non-aggregated carbonaceous fillers.

In the case where the welding is carried out by induction, then the composition P1 i comprises metal particles.

Advantageously, the welding is carried out by a laser system.

Regarding the composite reinforcing layer and the P2j thermoplastic polymer

One or more composite reinforcing layers may or may be present.

Each of said layers consists of a composition mainly comprising at least one thermoplastic polymer P2j, j corresponding to the number of layers present.

j is from 1 to 10, in particular from 1 to 5, in particular from 1 to 3, preferably j = 1. The term “predominantly” means that said at least one polymer is present in more than 50% by weight relative to the total weight of the composition.

Advantageously, said at least one major polymer is present at more than 60% by weight, in particular at more than 70% by weight, particularly at more than 80% by weight, more particularly greater than or equal to 90% by weight, relative to the weight total composition,

Said composition can also comprise impact modifiers and / or additives.

The additives can be selected from an antioxidant, a heat stabilizer, a UV absorber, a light stabilizer, a lubricant, an inorganic filler, a flame retardant, a nucleating agent, a plasticizer and a colorant.

Advantageously, said composition consists of said thermoplastic polymer P2j predominantly, from 0 to 5% by weight of impact modifier, from 0 to 5% by weight of additives, the sum of the constituents of the composition being equal to 100% (based on a max of P2j of 90%.

Said at least one majority polymer of each layer may be identical or different. In one embodiment, a single majority polymer is present at least in the composite reinforcing layer welded to the waterproofing layer.

In one embodiment, each reinforcing layer comprises the same type of polymer, in particular a polyamide.

P2j thermoplastic polymer

The term thermoplastic, or thermoplastic polymer, is understood to mean a material which is generally solid at room temperature, which may be semi-crystalline or amorphous, in particular semi-crystalline and which softens during an increase in temperature, in particular after passing its temperature of glass transition (Tg) and flows at a higher temperature when it is amorphous, or may present a clear melting at the passage of its so-called melting temperature (Tf) when it is semi-crystalline, and which becomes solid again during 'a decrease in temperature below its crystallization temperature, Te, (for a semi-crystalline) and below its glass transition temperature (for an amorphous).

Tg, Te and Tf are determined by differential scanning calorimetry (DSC) according to standard 11357-2: 2013 and 11357-3: 2013 respectively.

The polymer P2j of the composition of at least one of said composite reinforcing layers is such that its Tg is greater than the maximum temperature of use (Tu) of said structure and in particular, the Tg> Tu + 20 ° C, in particular Tg> Tu + 30 ° C.

In one embodiment, the polymer P2j has a Tg> Tu + 20 ° C, in particular Tg> Tu + 30 ° C, whatever the position of said reinforcing layer. In another embodiment, said reinforcing layer consisting of a composition comprising the polymer P2j having a Tg> Tu + 20 ° C, in particular Tg> Tu + 30 ° C, is the layer welded to said sealing layer.

In one embodiment, the polymer P2j of the composition of at least one of said composite reinforcing layers is such that its Tg is greater than the maximum temperature of use (Tu) of said structure Tg> Tu + 20 ° C and said reinforcing layer consisting of a composition comprising the polymer P2j is the layer welded to said sealing layer.

In one embodiment, the polymer P2j of the composition of at least one of said composite reinforcing layers is such that its Tg is greater than the maximum temperature of use (Tu) of said structure Tg> Tu + 30 ° C and said reinforcing layer consisting of a composition comprising the polymer P2j is the layer welded to said sealing layer.

In another embodiment, said reinforcing layer consisting of a composition comprising the polymer P2j has a Tg> Tu + 20 ° C, in particular Tg> Tu + 30 ° C, is the outermost reinforcing layer of the structure . The number-average molecular mass Mn of said thermoplastic polymer is preferably in a range of 10,000 to 40,000, preferably 12,000 to 30,000. These Mn values may correspond to inherent viscosities greater than or equal to 0.8 as determined in the m-cresol according to the ISO 307: 2007 standard but by changing the solvent (use of m-cresol in place of sulfuric acid and the temperature being 20 ° C).

polyamides, in particular comprising an aromatic structure and / or

cycloaliphatic, including copolymers, for example polyamide-polyethers, polyesters,

polyaryletherketones (PAEK),

polyetherether ketones (PEEK),

polyetherketone ketones (PEKK),

polyetherketoneetherketone ketones (PEKEKK),

polyimides, in particular polyetherimides (PEI) or polyamide-imides, polylsulfones (PSU) in particular polyarylsulfones such as polyphenylsulfones

(PPSU),

polyethersulfones (PES).

semi-crystalline polymers are more particularly preferred, and in particular polyamides and their semi-crystalline copolymers. The nomenclature used to define polyamides is described in standard ISO 1874-1: 201 1 "Plastics - Polyamide materials (PA) for molding and extrusion - Part 1: Description", in particular on page 3 (tables 1 and 2) and is well known to those skilled in the art.

The polyamide can be a homopolyamide or a copolyamide or a mixture thereof. Advantageously, the semi-crystalline polyamides are semi-aromatic polyamide, in particular a semi-aromatic polyamide of formula X / YAr, as described in EP1505099, in particular a semi-aromatic polyamide of formula A / XT in which A is chosen from a unit obtained from an amino acid, a unit obtained from a lactam and a unit corresponding to the formula (diamine in Ca). (Cb diacid), with a representing the number of carbon atoms of the diamine and b representing the number of carbon atoms of the diacid, a and b each being between 4 and 36,

advantageously between 9 and 18, the unit (diamine in Ca) being chosen from aliphatic diamines, linear or branched, cycloaliphatic diamines and alkylaromatic diamines and the unit (Cb diacid) being chosen from aliphatic, linear or branched diacids, cycloaliphatic diacids and aromatic diacids;

XT denotes a unit obtained from the polycondensation of a Cx diamine and terephthalic acid, with x representing the number of carbon atoms of the Cx diamine, x being between 5 and 36, advantageously between 9 and 18, in particular a polyamide of formula A / 5T, A / 6T, A / 9T, A / 10T or A / 1 1 T, A being as defined above, in particular a polyamide chosen from a PA MPMDT / 6T , one PA11 / 10T, one PA 5T / 10T, one PA 11 / BACT, one PA 1 1 / 6T / 10T, one PA MXDT / 10T, one PA MPMDT / 10T, one PA

BACT / 10T, one PA BACT / 6T, PA BACT / 10T / 6T, one PA 1 1 / BACT / 6T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 11 / BACT / 10T, one PA 11 / MXDT / 10T, a 1 1 / 5T / 10T.

T corresponds to terephthalic acid, MXD corresponds to m-xylylenediamine, MPMD corresponds to methylpentamethylene diamine and BAC corresponds to

bis (aminomethyl) cyclohexane. Said semi-aromatic polyamides defined above have in particular a Tg greater than or equal to 80 ° C.

Advantageously, each composite reinforcing layer consists of a composition comprising the same type of polymer, in particular a polyamide.

Advantageously, said composition comprising said polymer P2j is transparent to radiation suitable for welding.

Thermoplastic polymers are generally transparent for the purposes of welding, in particular laser. The carbonaceous nanofillers make it possible to impart a black color to a layer of a composition comprising a thermoplastic polymer, while maintaining the transparency to laser radiation of said layer.

Advantageously, the carbonaceous nanofillers are not agglomerated or not aggregated. Advantageously, the carbonaceous nanofillers are incorporated into the composition in an amount of 100 ppm to 500 ppm, and preferably of 100 ppm to 250 ppm.

Advantageously, the carbon nanofillers are chosen from carbon nanotubes (CNTs), carbon nanofibers, graphene, nanometric carbon black, and mixtures thereof.

Advantageously, the carbonaceous nanofillers are devoid of nanometric carbon black.

In one embodiment, the welding is carried out by a system chosen from among the laser, IR heating or induction heating.

Advantageously, the welding is carried out by a laser system.

Advantageously, the laser radiation is infrared laser radiation, and preferably has a wavelength of between 700 nm and 1200 nm and preferably between 800 nm and 1100 nm.

Regarding the structure

Said multilayer structure therefore comprises at least one sealing layer and at least one composite reinforcing layer which are welded.

In one embodiment, in said multilayer structure, each polymer P1 i of each sealing layer is partially or totally miscible with each polymer P1 i of the adjacent layer (s), each polymer P2j of each reinforcing layer is partially or totally miscible with each polymer P2j of the adjacent layer (s), and each polymer P2j is partially or totally miscible with each PU polymer when they are adjacent, and the polymer P21 is partially or totally miscible with the polymer P11 which is adjacent to it, the total or partial miscibility of said polymers being defined by the difference in glass transition temperature of the two resins, in the mixture, related to the difference in glass transition temperature of the two resins, before mixing, and the miscibility being total when said difference is equal to 0, and miscibility being partial, when said difference is different from 0, an immiscibility of the polymer P2j with the polymer PU being excluded.

When the miscibility of said polymers is partial said difference is said miscibility is greater than said difference is small.

Advantageously, when the miscibility of said polymers is partial, said difference is less than 30%, preferably less than 20%, in absolute value.

In one embodiment, the glass transition temperature (s) of the mixture, depending on whether the miscibility is total or partial, which must be between the glass transition temperatures of said polymers before mixing and different from them, by at least 5 ° C, preferably at least 10 ° C. The expression “completely miscible” means that when, for example, two polymers P11 and PI2 having respectively a Tg1 i and a Tgl2 _, are respectively present in two sealing layers or two adjacent reinforcing layers, then the mixture of the two polymers does not has only one Tg1112 whose value is between Tg11 and a Tg1 _2.

This Tg11I2 value is then greater than Tg1 i by at least 5 ° C, in particular by at least 10 ° C and lower than Tgl2 by at least 5 ° C, in particular by at least 10 ° C.

The expression "partially miscible" means that when, for example, two polymers P1 i and PI2 having respectively a Tg1 i and a Tgl2, are present

respectively in two waterproofing layers or two adjacent reinforcing layers, then the mixture of the two polymers has two Tg: Tg'1 i and Tg'1 ₂ , with Tg1 i <Tg'1 i <Tg'1 ₂ <Tg1 ₂ .

These Tg'1 i and Tg '^ values are then greater than Tg1 i by at least 5 ° C, in particular by at least 10 ° C and below Tgl2 by at least 5 ° C, in particular by minus 10 ° C.

An immiscibility of two polymers results in the presence of two Tg, Tg1 i and Tgl2 _, in the mixture of the two polymers which correspond to the respective Tg Tg1 i and Tgl2 of the pure polymers taken separately.

Advantageously, said welded sealing and reinforcing layers consist of compositions which respectively comprise different polymers.

However, said different polymers can be of the same type.

Thus, if one of the two welded composite waterproofing and reinforcing layers consists of a composition comprising an aliphatic polyamide, then the other layer consists of a composition comprising a polyamide which is not aliphatic and which is for example a semi-aromatic polyamide so as to have a high tg polymer as the matrix of the composite reinforcement.

Said multilayer structure can include up to 10 waterproofing layers and up to

10 layers of composite reinforcement.

It is obvious that said multilayer structure is not necessarily symmetrical and that it can therefore include more sealing layers than composite layers or vice versa.

Advantageously, said multilayer structure comprises one, two, three, four, five, six, seven, eight, nine or ten sealing layers and one, two, three, four, five, six, seven, eight, nine or ten layers composite reinforcement.

Advantageously, said multilayer structure comprises one, two, three, four or five sealing layers and one, two, three, four or five composite reinforcement layers. Advantageously, said multilayer structure comprises one, two or three sealing layers and one two or three composite reinforcement layers. Advantageously, they consist of compositions which comprise

respectively different polymers.

Advantageously, they consist of compositions which comprise

polyamides corresponding to polyamides P1 i and P2j respectively.

Advantageously, they consist of compositions which comprise

different polyamides respectively.

In one embodiment, said multilayer structure comprises a single waterproofing layer and several reinforcing layers, said waterproofing layer being welded to said adjacent reinforcing layer.

In another embodiment, said multilayer structure comprises a single reinforcing layer and a plurality of sealing layers, said reinforcing layer being welded to said adjacent sealing layer.

In an advantageous embodiment, said multilayer structure comprises a single sealing layer and a single composite reinforcing layer which are welded. All combinations of these two layers are therefore within the scope of the invention, provided that at least said innermost composite reinforcing layer is welded to said outermost adjacent waterproofing layer, the other layers being welded. between them or not.

Advantageously, in said multilayer structure, each sealing layer consists of a composition comprising the same type of polymer P1 i, in particular a polyamide.

By the same type of polymer is meant for example a polyamide which can be an identical or different polyamide depending on the layers.

Advantageously, said polymer P1 i is a polyamide and said polymer P2j is a polyamide.

Advantageously, the polyamide P1 i is identical for all the waterproofing layers. Advantageously, said polymer P1 i is a long-chain aliphatic polyamide, in particular PA1010, PA 1012, PA 1212, PA11, PA12, in particular PA 11 or PA12.

Advantageously, the polyamide P1 i is a long-chain semi-aromatic polyamide, in particular PA 11 / 5T, PA 1 1 / 6T or PA 11 / 10T. Obviously in this case, the level of 11 must be chosen judiciously so that the Tm of said polymers is less than 280 ° C, preferably 265 ° C.

Advantageously, in said multilayer structure, each reinforcing layer consists of a composition comprising the same type of polymer P2j, in particular a polyamide.

Advantageously, the P2j polyamide is identical for all the reinforcing layers. Advantageously, said polymer P2j is a semi-aromatic polyamide, in particular chosen from a PA MPMDT / 6T, a PA 1 1/1 OT, a PA 1 1 / BACT, a PA 5T / 10T, a PA 11 / 6T / 10T , one PA MXDT / 10T, one PA MPMDT / 10T, one PA BACT / 10T, one PA BACT / 6T,

PA BACT / 10T / 6T, one PA 11 / BACT / 6T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 1 1 / BACT / 10T, one PA 1 1 / MXDT / 10T and one PA 5T / 10T.

Advantageously, in said multilayer structure, each sealing layer consists of a composition comprising the same type of polymer P1 i, in particular a polyamide, and each reinforcing layer consists of a composition comprising the same type of polymer P2j, in particular a polyamide, provided that the polyamides P1 i and P2j are different, that is to say that if the sealing layer (s) is or consist (s) of compositions comprising a long-chain aliphatic polyamide then the or the waterproofing layers are or consist of compositions comprising a semi-aromatic polyamide.

Advantageously, said polymer P1 i is a long-chain aliphatic polyamide, in particular PA1010, PA 1012, PA 1212, PA11, PA12, in particular PA 11 or PA12 and said polymer P2j is a semi-aromatic polyamide, in particular chosen from a PA MPMDT / 6T, one PA PA11 / 10T, one PA 11 / BACT, one PA 5T / 10T, one PA 11 / 6T / 10T, one PA MXDT / 10T, one PA MPMDT / 10T, one PA BACT / 10T, one PA BACT / 6T, PA BACT / 10T / 6T, one PA 11 / BACT / 6T, PA 1 1 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 11 / BACT / 10T, one PA 1 1 / MXDT / 10T and a 5T / 10T PA.

Advantageously, said multilayer structure consists of a single reinforcing layer and a single sealing layer in which said polymer P1 i is a long-chain aliphatic polyamide, in particular PA1010, PA 1012, PA 1212, PA1 1, PA12, in particular PA 11 or PA12 and said polymer P2j is a semi-aromatic polyamide, in particular chosen from a PA MPMDT / 6T, a PA PA1 1 / 10T, a PA 11 / BACT, a PA 1 1 / 6T / 10T, one PA MXDT / 10T, one PA MPMDT / 10T, one PA BACT / 10T, one PA BACT / 6T, PA BACT / 10T / 6T, one PA 11 / BACT / 6T, PA 1 1 / MPMDT / 6T, PA

1 1 / MPMDT / 10T, PA 11 / BACT / 10T, one PA 1 1 / MXDT / 10T.

According to one embodiment, said multilayer structure is a reservoir.

According to another embodiment, said multilayer structure is a flexible pipe.

The maximum temperature of use Tu of said multilayer structure is greater than 50 ° C, in particular greater than 100 ° C.

In one embodiment, said multilayer structure defined above exhibits resistance to decompression and suitability for drying.

In fact, in the case of the storage or transport of hydrogen, the hydrogen can diffuse through the sealing layer (s), from the inside of the tube or the tank towards the interface between the last layer of 'waterproofing and the first layer of composite reinforcement, due to the permeability of the sealing layer or layers to transported or stored hydrogen. The accumulation of hydrogen at this location can generate a pressure which will lead to buckling (collapse) of the sealing layer (s), when the pressure inside the tube or the tank will be lower than the pressure at the interface with the composite reinforcement, which may occur in particular when the pumping or transport of hydrogen is stopped during a production shutdown which leads to a pressure drop of several hundred bars at atmospheric pressure or when the tank of storage will be empty. The same is true during the proof tests of tanks under internal water pressure: this water is liable to migrate by permeation, at the interface between the composite reinforcement and the last layer of waterproofing and will subsequently be very difficult to remove, resulting in long and expensive drying cycles of said storage tanks, in particular under vacuum.

In another embodiment, said multilayer structure defined above further comprises a metal carcass located inside the sealing layer. This metallic carcass is not waterproof and corresponds to the innermost layer. Advantageously, said multilayer structure further comprises at least one outer layer, in particular metallic, said layer being the outermost layer of said multilayer structure.

Said outer layer is a second reinforcing layer but metallic and not composite.

There may also be on the structure a polymeric protective layer (outermost layer) which notably has an anti-abrasion role or which makes it possible to put an inscription on the structure.

Regarding the fibrous material

Regarding the constituent fibers of said fibrous material, they are in particular fibers of mineral, organic or plant origin.

Advantageously, said fibrous material can be sized or not sized.

Said fibrous material can therefore comprise up to 0.1% by weight of an organic material (thermosetting or thermoplastic resin type) called sizing.

Among the fibers of mineral origin, mention may be made of carbon fibers, glass fibers, basalt 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 a thermoplastic or thermosetting polymer, such as semi-aromatic polyamide fibers, aramid fibers or polyolefin fibers, for example. Preferably, they are based on an amorphous thermoplastic polymer and have a glass transition temperature Tg greater than the Tg of the polymer or mixture of thermoplastic polymer of constitution of the prepregnation matrix when the latter is amorphous, or greater than the Tm of the polymer or mixture of thermoplastic polymer of constitution of the prepregnation matrix when the latter is semi-crystalline. Advantageously, they are based on a semi-crystalline thermoplastic polymer and have a melting point Tm greater than the Tg of the polymer or mixture of thermoplastic polymer constituting the pre-impregnation matrix when the latter is amorphous, or greater than the Tm of the polymer or mixture of thermoplastic polymer constituting the prepreg matrix when the latter is semi-crystalline. Thus, there is no risk of fusion for the organic fibers constituting the fibrous material during impregnation with the thermoplastic matrix of the final composite. Among the fibers of plant origin, mention may be made of natural fibers based on flax, hemp, lignin, bamboo, silk, especially spider silk, sisal, and other cellulose fibers, in particular viscose. These fibers of plant origin can be used pure, treated or else coated with a coating layer, with a view to facilitating the adhesion and impregnation of the thermoplastic polymer matrix.

The fibrous material can also be a fabric, braided or woven with fibers.

It can also correspond to fibers with retaining threads.

These constitution fibers can be used alone or in mixtures. Thus, organic fibers can be mixed with mineral fibers in order to be pre-impregnated with thermoplastic polymer powder and to form the pre-impregnated fibrous material.

The rovings of organic fibers can have several grammages. They can also have several geometries. The fibers constituting the fibrous material may also be in the form of a mixture of these reinforcing fibers of different geometries. Fibers are continuous fibers.

Preferably, the fibrous material consists of continuous carbon or glass fibers or their mixture, in particular carbon fibers. It is used as a wick or several wicks.

According to another aspect, the present invention relates to a method for manufacturing a multilayer structure as defined above, characterized in that it comprises a step of welding the reinforcing layer as defined above to the layer of sealing as defined above.

Advantageously, the soldering step is carried out by a system chosen from among the laser, infrared heating (IR), heating by LED, heating by induction or by layers or high frequency heating (HF).

Advantageously, said method comprises a step of extruding said sealing layer on a metal carcass and a step of welding the reinforcing layer on the sealing layer. According to another aspect, the present invention relates to the use of a multilayer structure chosen from a tank or pipe or tube comprising, from the inside to the outside, at least one sealing layer as defined above and at least one composite reinforcing layer as defined above,

said at least one thermoplastic polymer of each sealing layer possibly being the same or different, and at least one of said composite reinforcing layers consisting of a fibrous material in the form of continuous fibers impregnated with a composition mainly comprising at least a thermoplastic polymer P2j, (j = 1 to m, m being the number of reinforcement layers) in particular semi-crystalline, said thermoplastic polymer P2j having a Tg, as measured according to ISO 1 1357-3: 2013, greater than the maximum temperature of use of said structure (Tu), with Tg> Tu + 20 ° C, in particular Tg> Tu + 30 ° C, Tu being greater than 50 ° C, in particular greater than 100 ° C,

for the preparation of a tank or pipe or tube for the transport, distribution or storage of hydrogen.

EXAMPLES

In all the examples, the reservoirs are obtained by rotational molding of the liner at a temperature suited to the nature of the thermoplastic resin used, but in all cases below 280 ° C.

In the case of epoxy, a wet filament winding process is then used which consists in winding fibers around the liner, which fibers are pre-impregnated in a bath of liquid epoxy. The reservoir is then polymerized in an oven for 2 hours.

In all other cases, a fibrous material is then used which has been impregnated with the thermoplastic resin (tape). This tape is deposited by filament winding using a robot comprising a 1500W power laser heater at a speed of 12m / min and there is no polymerization step.

Example (counter example):

Type IV hydrogen storage tank, composed of an epoxy composite reinforcement (Tg 80 ° C) carbon fibers T700SC31 E (produced by Toray) and a layer sealing in PA6. : no miscibility between the 2 resins (see table 1) which prevents any welding between the fiber reinforcement and the waterproofing layer.

Example 2 (counter example):

Type IV hydrogen storage tank, composed of an epoxy composite reinforcement (Tg 80 ° C) T700SC31 E carbon fibers (produced by Toray) and a layer

waterproofing in HDPE. : no miscibility between the 2 resins (see Table 1) which prevents any welding between the fiber reinforcement and the waterproofing layer.

Example 3: Hydrogen storage tank of type between IV and V, composed of a reinforcement in BACT / 10T carbon fiber T700SC31 E composite (produced by Toray) and a sealing layer in PA6: good partial miscibility between the 2 resins (see table I) which allows a good weld between the fibrous reinforcement and the waterproofing layer.

The BACT / 10T type composition chosen has a melting point, Tm, of 283 ° C, a crystallization temperature, Te, of 250 ° C and a glass transition temperature of 164 ° C.

Example 4: Hydrogen storage tank of type between IV and V, composed of a reinforcement in BACT / 10T carbon fiber composite T700SC31 E (produced by Toray) and a sealing layer in PA66: good partial miscibility between the 2 resins (see table I) which allows a good weld between the fibrous reinforcement and the waterproofing layer. The BACT / 10T type composition chosen has a melting point, Tm, of 283 ° C, a crystallization temperature, Te, of 250 ° C and a glass transition temperature of 164 ° C. Tg, Te and Tf are determined by differential scanning calorimetry (DSC) according to 11357-2: 2013 and 11357-3: 2013 respectively.

The higher melting point of the PA66 liner (268.8 ° C) compared to the PA6 liner (220 ° C) of Example 3, facilitates the application of the tape and the manufacture of the tank.

Example 5: Hydrogen storage tank of type between IV and V, composed of a reinforcement in composite 1 1 / BACT / 10T carbon fibers CT24-5.0 / 270-T140 (produced by SGL Carbon) and a layer sealing in PA1 1: good partial miscibility between the 2 resins (see Table 1) which leads to good welding between the fiber reinforcement and the sealing layer. The composition of type 11 / BACT / 10T chosen exhibits a melting point, Tm, of 280 ° C, a crystallization temperature, Te, of 220 ° C and a glass transition temperature of 160 ° C. The Tg, Te and Tf are determined by differential scanning calorimetry (DSC) according to standard 11357-2: 2013 and 11357-3: 2013 respectively.

Example 6: Hydrogen storage tank of type between IV and V, composed of a reinforcement in composite 1 1 / BACT / 10T carbon fibers CT24-5.0 / 270-T140 (produced by SGL Carbon) and a waterproofing layer in PA1 1/1 OT: good partial miscibility between the 2 resins (see table 1) which leads to a good weld between the fiber reinforcement and the waterproofing layer.

The type 1 1 / BACT / 10T composition chosen has a melting point, Tm, of 280 ° C, a crystallization temperature, Te, of 220 ° C and a glass transition temperature of 160 ° C. The Tg, Te and Tf are determined by differential scanning calorimetry (DSC) according to standard 11357-2: 2013 and 11357-3: 2013 respectively.

The composition of 1 1/1 OT used for the liner leads to a Tm of 255 ° C.

The fact of using a 1 1/1 OT liner with a melting point of 255 ° C, close to that of the 1 1 / BACT / 10T resin used as the matrix of the composite, facilitates the use of the tank.

Example 7: Hydrogen storage tank of type between IV and V, composed of a reinforcement in composite 1 1 / BACT carbon fibers CT24-5.0 / 270-T140 (produced by SGL Carbon) and a layer of waterproofing in PA1 1: good partial miscibility between the 2 resins (see Table 1) which leads to good welding between the fibrous reinforcement and the waterproofing layer. The type 1 1 / BACT composition chosen has a melting point, Tm, of 278 ° C, a crystallization temperature, Te, of 210 ° C and a glass transition temperature of 157 ° C. The Tg, Te and Tf are determined by differential scanning calorimetry (DSC) according to standard 11357-2: 2013 and 11357-3: 2013 respectively.

The fact of using a polymer of type 1 1 / BACT which crystallizes slowly, makes it possible to lower the processing temperatures of the tape compared with the 1 1 / BACT / 10T of the previous example and facilitates the use of a PA1 liner 1.

Example 8: Hydrogen storage tank of type between IV and V, composed of a reinforcement in composite 1 1 / BACT carbon fibers CT24-5.0 / 270-T140 (produced by SGL Carbon) and a layer of waterproofing in PA1 1 / 10T: good partial miscibility between the 2 resins (see table 1) which leads to good welding between the fiber reinforcement and the waterproofing layer.

The type 1 1 / BACT composition chosen has a melting point, Tm, of 278 ° C, a crystallization temperature, Te, of 210 ° C and a glass transition temperature of 157 ° C. The Tg, Te and Tf are determined by differential scanning calorimetry (DSC) according to standard 11357-2: 2013 and 11357-3: 2013 respectively.

The composition of 1 1 / 10T used for the liner leads to a Tm of 255 ° C.

The fact of using a 1 1/1 OT liner, the melting point of which is 255 ° C., close to 1 1 / BACT which constitutes the reinforcing resin of the composite, facilitates the use of the tank. In all the examples in Table 1 below, to evaluate the miscibility of the resins, the mixtures were made from powders with a particle size of about 150 μm on micro-DSM with a recirculation time of 1 minute after fusion. All mixtures were made at 300 ° C except for the epoxy-polyethylene mixture which was made at 220 ° C.

At the end of the mixing, the mixture is injected into a mold to make a test specimen which will be characterized as DMA.

[Table 1]

^*** Tg measurements are made by DMTA according to ISO 4664 1

Miscibility test results: - column 4: glass transition temperature of each resin before mixing

- column 5: glass transition temperature of the resins in the mixture

- column 6: ratio between the glass transition temperature differences of the resins in the mixture and before the mixture.

100% indicates an immiscibility of the resins,

<80% indicates poor miscibility,

<30% indicates good, although partial, miscibility,

0 indicates full miscibility.

Claims

1. Multilayer structure chosen from a tank, a pipe or tube, intended for the transport, distribution or storage of hydrogen, comprising, from the inside to the outside, at least one sealing layer and at least a composite reinforcing layer,

said sealing layers consisting of a composition mainly comprising at least one thermoplastic polymer P1 i (i = 1 to n, n being the number of sealing layers) semi-crystalline whose Tf, as measured according to ISO 11357 -3: 2013, is less than 280 ° C, in particular less than 265 ° C, said at least one thermoplastic polymer of each sealing layer possibly being the same or different, and at least one of said composite reinforcement layers consisting of a fibrous material in the form of continuous fibers impregnated with a composition predominantly comprising at least one polymer

thermoplastic P2j, (j = 1 to m, m being the number of reinforcing layers) in particular semi-crystalline, said thermoplastic polymer P2j having a Tg, as measured according to ISO 11357-3: 2013, greater than the maximum temperature d 'use of said structure (Tu), with Tg> Tu + 20 ° C, in particular Tg> Tu + 30 ° C, Tu being greater than 50 ° C, in particular greater than 100 ° C.

2. Multilayer structure according to claim 1 wherein each polymer P1 i of each sealing layer is partially or completely miscible with each polymer P1 i of the adjacent layer (s), each polymer P2j of each reinforcing layer is partially or completely miscible with each polymer P2j of the adjacent layer (s), and the polymer P21 is

partially or totally miscible with the polymer P1 1 which is adjacent to it, the total or partial miscibility of said polymers being defined by the difference in glass transition temperature of the two resins, in the mixture, related to the difference in glass transition temperature of the two resins, before mixing, and the miscibility being total when the said difference is equal to 0, and the miscibility being partial, when the said difference is other than 0.

3. Multilayer structure according to one of claims 1 or 2, characterized in that each sealing layer comprises the same type of polymer, in particular a polyamide.

4. Multilayer structure according to one of claims 1 or 2, characterized in that each reinforcing layer comprises the same type of polymer, in particular a polyamide.

5. Multilayer structure according to one of claims 3 or 4, characterized in that each sealing layer comprises the same type of polymer, in particular a polyamide and each reinforcing layer comprises the same type of polymer, in particular a polyamide. .

6. Multilayer structure according to one of claims 1 to 5, characterized in that

that it has a single layer of waterproofing and a single layer of reinforcement.

7. Multilayer structure according to one of claims 1 to 6, characterized in that said structure is a reservoir or a flexible pipe.

8. Multilayer structure according to one of claims 1 to 7, characterized in that said composition comprising said polymers P1 and P2 also comprises additives, such as carbon blacks, carbon nanotubes (CNTs) or graphenes allowing them absorb radiation suitable for welding.

9. Multilayer structure according to one of claims 1 to 8, characterized in that said composition comprising said polymer P2j is transparent to a

radiation suitable for welding.

10. Multilayer structure according to claim 8 or 9, characterized in that the

welding is carried out by a system chosen from among the laser, infrared heating (IR), heating by led, heating by induction or by layers or high frequency heating (HF).

1 1. Multilayer structure according to one of claims 1 to 10, characterized in that said polymer P1 i is a polyamide.

12. Multilayer structure according to one of claims 1 to 10, characterized in that said polymer P2j is a polyamide.

13. Multilayer structure according to one of claims 11 or 12, characterized in that said polymer P1 i and said polymer P2j are polyamides.

14. Multilayer structure according to claim 1 1 or 13, characterized in that said polymer P1 i is a long-chain aliphatic polyamide, in particular PA1010, PA 1012, PA 1212, PA11, PA12, in particular PA 11 or PA12 or semi- aromatic, in particular PA 11 / 5T, PA 1 1 / 6T and PA1 1 / 10T.

15. Multilayer structure according to claim 12 or 13, characterized in that said polymer P2j is a semi-aromatic polyamide, in particular chosen from a PA MPMDT / 6T, a PA 1 1 / 10T, a PA 1 1 / BACT, a PA 5T / 10T one PA 11 / 6T / 10T, one PA MXDT / 10T, one PA MPMDT / 10T, one PA BACT / 10T, one PA BACT / 6T, PA

BACT / 10T / 6T, one PA 1 1 / BACT / 6T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA

1 1 / BACT / 10T, one PA 1 1 / MXDT / 10T, one PA11 / 5T / 10T.

16. Multilayer structure according to one of claims 13 to 15, characterized in that said polymer P1 i is a long-chain aliphatic polyamide, in particular PA1010, PA 1012, PA 1212, PA11, PA12, or semi-aromatic, in in particular PA 1 1 / 5T, or PA 11 / 6T or PA 1 1 / 10T, in particular PA 1 1 or PA12 and said polymer P2j is a semi-aromatic polyamide, in particular chosen from a PA MPMDT / 6T, a PA PA1 1 / 10T, one PA 11 / BACT, one PA 5T / 10T, one PA 1 1 / 6T / 10T, one PA MXDT / 10T, one PA MPMDT / 10T, one PA BACT / 10T, one PA BACT / 6T, PA BACT / 10T / 6T, one PA

1 1 / BACT / 6T, PA 11 / MPMDT / 6T, PA 1 1 / MPMDT / 10T, PA 11 / BACT / 10T, one PA 1 1 / MXDT / 10T, one PA11 / 5T / 10T.

17. A multilayer structure according to one of claims 1 to 16, characterized in that it exhibits resistance to decompression and suitability for drying.

18. Multilayer structure according to one of claims 1 to 17, characterized in that said structure further comprises a metal frame located inside the sealing layer.

19. Multilayer structure according to one of claims 1 to 18, characterized in that said structure further comprises at least one outer layer, in particular metallic, said layer being the outermost layer of said structure

multilayer.

20. Multilayer structure according to one of claims 1 to 19, characterized in that the fibrous material is chosen from glass fibers and carbon or basalt fibers or based on basalt.

21. A method of manufacturing a multilayer structure as defined in one of claims 1 to 20, characterized in that it comprises a step of welding the reinforcing layer as defined in claim 1 on the layer of sealing as defined in claim 1.

22. The method of claim 21, characterized in that the soldering step is carried out by a system chosen from among the laser, infrared heating (IR), heating by led, heating by induction or by layers or high frequency heating (HF).

23. The method of claim 21 or 22, characterized in that it comprises a step of extruding said sealing layer on a metal carcass and a step of welding the reinforcing layer on the sealing layer.