Pressurized gas tank including a protective coating

Abstract

The pressurized gas tank (2) defines an interior volume for storing a pressurized gas. It comprises: - a reinforcing envelope (4) made of a composite material comprising reinforcing fibers and / or particles, the reinforcing envelope (4) comprising a central cylindrical portion, - a protective covering (5) slipped onto the central cylindrical portion of the reinforcing envelope (4), the protective covering (5) comprising at least a first protective layer formed by a first continuous seamless protective sleeve (6), the first protective sleeve (6) being made with one or more heat-shrinkable polymers, the protective covering (5) being configured to provide mechanical, chemical and / or fire protection. Figure for abstract: figure 2

Description

Title of the invention: Pressurized gas tank comprising a protective coating Technical field

[0001] The invention relates to the field of pressure tanks, in particular for a vehicle. The invention relates more particularly to a pressurized gas tank for a vehicle, as well as a vehicle comprising such a pressurized gas tank, as well as a method for protecting a pressurized gas tank. Technological background

[0002] Pressure gas tanks are used to store and transport any type of pressurized gas. Pressure gas tanks are generally classified into one of five types: a so-called Type I pressure gas tank having an all-metal construction; a so-called Type II pressure gas tank having a metal construction including a fiber winding for reinforcement of its cylindrical portion; a so-called Type III pressure gas tank having a metal liner with a composite reinforcing structure; a so-called Type IV pressure gas tank including a plastic liner with a composite reinforcing structure; and a so-called Type V pressure gas tank having a composite reinforcing structure and being without a liner.

[0003] Thus, a pressurized gas tank is already known in the prior art, for example configured to store gas at a pressure of at least 350 bar or at least 700 bar, the gas being, for example, hydrogen (H2). This pressurized gas tank is configured to be used by a vehicle equipped with the pressurized gas tank for various functions, as an energy source. This tank is usually made of composite material for reasons of weight saving and safety.

[0004] Such a pressurized gas tank is conventionally composed of an internal envelope called a liner, which has a sealing function with respect to the gas contained in the tank. The liner is, for example, made of a plastic material, in the case of a type IV tank, chosen for its lightness and low manufacturing cost, or of a metal such as aluminum, or of another material such as a metal alloy, in the case of a type III tank. The “plastic” type liner comprises at least one opening for filling and emptying the tank. It is manufactured by injection or rotational molding or by extrusion-blow molding of a thermoplastic or thermosetting polymer material such as, for example, polyethylene, polyamide, polyphthalamide, polyurethane, silicone, polyoxymethylene. Advantageously, in the context of a Type IV tank, the plastic chosen for the liner can be filled with fibers, particles of nanometric or micrometric size, or even be composed of several layers. The reinforcing fibers are, for example, glass fibers, carbon fibers, basalt fibers, aramid fibers, polymer fibers, silica fibers, polyethylene fibers, natural fibers, metal fibers, metal alloy fibers or ceramic fibers. The particles can be chosen from different types of materials, such as ceramics, glass, metals, organic materials, or a combination thereof. These fillers make it possible to increase the resistance to deformation of the composite material. In a polymer material filled with reinforcing fibers, the reinforcing fibers and the polymer material are entangled to form a single-piece material.In addition to reinforcing fibers, it is also possible to integrate other fillers such as reinforcing particles such as graphene particles, CSR particles (for "core-shell rubber") or carbon nanotubes. In the case of a stack of several layers, these can be obtained from different materials, such as metals or organic materials. This multi-layer approach makes it possible to reduce the gas permeability of the liner. Both approaches mentioned can be combined.

[0005] The liner is generally generally cylindrical in shape and has two dome-shaped or hemispherical ends. The liner has an opening, which is generally surmounted by a gas filling / dispensing nozzle. The pressurized fluid exerts high stresses on the internal surface of the liner, which can affect the integrity of the liner and cause dangerous leaks, particularly with combustible gases such as hydrogen.

[0006] To improve the mechanical properties of the pressurized gas tank, the liner is surrounded by a composite reinforcing structure, generally made by winding around the liner strips of fibers impregnated with a resin, at different angles.

[0007] Conventionally, in order to protect the composite reinforcement structure against environmental elements (temperature, water, radiation, UV, ozone, chemical attacks, etc.), an additional protective layer is added to the exterior of the tank to provide resistance to chemical, mechanical and / or thermal attacks. This generally consists of either a layer of glass fibers impregnated with intumescent resin (applied by filament winding in a dry or wet process), an intumescent coating generally based on two-component epoxy (2K) applied by spraying, direct dosing or injection, or a combination of the two. The epoxy-based protective layer contains intumescent agents which, after exposure to fire, expand and create a barrier insulating. The expansion and calcination of the resin by the intumescent reaction reduces and slows down the heat transfer from the flames to the composite reinforcement structure, thus delaying the rise in temperature of the composite reinforcement structure and, consequently, the decomposition of the resin of the composite reinforcement structure. This phenomenon allows the rapid emptying equipment installed on the tank nozzles to purge the tank and prevent its failure, for example, by rupture of the composite reinforcement structure.

[0008] However, such protective layers do not guarantee a satisfactory level of protection of the composite reinforcement structure at minimum thicknesses due to their intrinsic fragility. For example, the formation of post-impact cracks creates a path allowing, among other things, chemicals to come into contact with the composite reinforcement structure and therefore corrode it. This corrosion increases the risk of tank failure. This post-impact cracking phenomenon is exacerbated at negative temperatures.

[0009] Furthermore, the epoxy-based protective layer does not have the capacity to absorb impacts at low temperatures. In addition, the epoxy-based protective layer requires long curing times at room temperature, which results, during the manufacture of the tank, in the use of an oven to accelerate the curing and therefore increases the costs. Furthermore, this delay in curing does not allow the desired properties of the epoxy-based protective layer (resistance to chemical, mechanical and / or thermal attacks) and of the contact surface between the epoxy-based protective layer and the composite reinforcement structure to be obtained, which can cause the aforementioned defects.

[0010] It is therefore desirable to have a protective layer capable of withstanding the chemical, mechanical and thermal stresses imposed on the tank, over wide temperature ranges, and not exhibiting these drawbacks. It is further desirable for the protective layer to have these properties while being relatively light.

[0011] One solution proposed has been to use protective layers based on polyureas. Although effective, this solution has the disadvantage of adding mass and volume that may be considered too great by some manufacturers. In addition, the processes for depositing polyurea layers are complex to implement.

[0012] Thus, an aim of the invention is to provide a protective coating for a pressurized gas tank capable of resisting the chemical, mechanical and thermal stresses imposed on the tank, and this, in wide ranges of temperature. It is also desirable that the protective coating has these properties while being relatively light and thin. Summary of the invention

[0013] To this end, the invention relates to a pressurized gas tank defining an internal volume for storing a pressurized gas and comprising: - a reinforcing envelope made of composite material comprising reinforcing fibers and / or particles, the reinforcing envelope comprising a central cylindrical part, characterized in that it further comprises: - a protective covering slipped over the central cylindrical portion of the reinforcing casing, the protective covering comprising at least a first protective layer formed by a first continuous seamless protective sleeve, the first protective sleeve being made with one or more heat-shrinkable polymers, the protective covering being configured to provide mechanical, chemical and / or fire protection.

[0014] The fact that the first protective sleeve is made of one or more heat-shrinkable polymers makes it easier to manufacture the tank. In particular, it is understood that to install the first protective sleeve, it is sufficient to insert the first protective sleeve, which has not yet been heat-shrunk, through one of the ends of the reinforcing jacket and then place it at the central cylindrical part of the reinforcing jacket. The first protective sleeve is then heated to a predetermined temperature in order to cause the first protective sleeve to heat-shrink. Thus, the installation of the protective coating is particularly simple and rapid. It is thus possible to provide mechanical, chemical and / or fire protection to the reinforcing jacket in a simple and inexpensive manner.

[0015] Preferably, the first protective sleeve is configured so that its diameter shrinks by 50% to 80% of its original diameter when heated to a temperature above 120°C, for example above 150°C, preferably about 200°C. Such temperatures advantageously make it possible to obtain a good level of shrinkage of the first protective sleeve while reducing the risk of damage to another part of the tank.

[0016] The use of a protective sleeve as a first protective layer makes it possible to precisely control the thickness of this first protective layer, unlike, for example, a protective layer which would be applied by spraying. Preferably, the protective layer(s) of the protective coating form(s) a wall having a thickness of between 0.5 and 12 mm, preferably between 0.5 and 8 mm, even more preferably between 0.5 and 3 mm.

[0017] Furthermore, the use of a protective sleeve makes it possible to control physical and chemical uniformity within the material comprising the protective sleeve. Finally, the shrinkage of the first protective sleeve during the manufacture of the tank makes it possible to apply pressure to the central cylindrical part of the reinforcing casing, which promotes the evacuation of air which could be trapped in the reinforcing casing, thus improving the mechanical resistance properties of the reinforcing casing.

[0018] By "heat-shrinkable polymer" is meant heat-shrinkable polymers or shape-memory polymers, which are generally crosslinked. These polymers advantageously make it possible to obtain levels of shrinkage such that the diameter of the first protective sleeve shrinks by 50% to 80% of its original diameter when it is heated above a predetermined temperature.

[0019] The reinforcing envelope is typically formed by winding strips of fibers impregnated with a resin, at different angles. The fibers used can be chosen from ceramics, glasses and organic materials. For example, carbon fibers, glass fibers, aramid fibers are commonly used. The resins considered can be thermosetting, photosetting or thermoplastic. For example, for thermosetting or photosetting resins, epoxy or vinylester type resins are used, and for thermoplastic resins, polyamide or polyetheretherketone (PEEK) type resins. The winding process can be carried out wet, with the fibers then dipping into a resin bath before being wound, or dry, with the fibers then being in the form of a strip of parallel fibers impregnated with resin, more commonly called "Tow preg".The resins used may be loaded with particles of nanometric and / or micrometric sizes in order to improve the properties of the composite reinforcement envelope. These particles may be based on a material chosen from ceramic materials, glasses, metals, organic materials or any combination thereof. For example, hollow glass beads may be used to lighten and reduce the risk of delamination of the fiber strips of the composite reinforcement structure, graphene or carbon nanotubes leading to an improvement in the properties of the composite reinforcement envelope from a mechanical, electrical or thermal point of view, and to a reduction in the risk of delamination of the fiber strips of the composite reinforcement envelope, rubber beads allowing an increase in ductility, a reduction . the risk of delamination of the fiber strips of the composite reinforcement envelope as well as a reduction of residual stresses within the composite reinforcement envelope.

[0020] According to a preferred embodiment, the pressurized gas tank is intended to contain pressurized hydrogen and to be used on a vehicle, such as a motor vehicle, a truck, a bus, a train, a construction machine or even a boat.

[0021] The invention may also include one or more of the following optional features taken alone or in combination.

[0022] Advantageously, the protective coating comprises at least a second protective layer formed by a second continuous seamless protective sleeve made with one or more heat-shrinkable polymers. In this way, it can be provided that each protective layer provides properties different from or complementary to the properties of the other layer. As for the first protective sleeve, the second protective sleeve is preferably configured so that its diameter shrinks by 50% to 80% of its original diameter when heated to a temperature above 120°C, for example above 150°C, preferably about 200°C. As indicated previously, such temperatures advantageously make it possible to obtain a good level of shrinkage of the second protective sleeve while reducing the risk of damage to another part of the tank.

[0023] According to one embodiment, the second protective sleeve is slipped at least partially onto the first protective sleeve. Thus, the areas of the tank in which the second protective sleeve is slipped onto the first protective sleeve benefit from both the protective characteristics provided by the first protective sleeve and the second protective sleeve. Preferably, the second protective sleeve is slipped onto the entire first protective sleeve.

[0024] Advantageously, the central cylindrical portion of the reinforcing casing is arranged between two longitudinal end portions of the reinforcing casing, the protective coating being further slipped onto at least one of the two longitudinal end portions of the reinforcing casing. In this way, in addition to the central cylindrical portion, it is possible to protect at least one of the longitudinal ends of the reinforcing casing with the protective coating. According to one embodiment, the protective coating is slipped onto the two longitudinal end portions of the reinforcing casing. It is then understood that the protective coating covers substantially a larger part of the reinforcement envelope, or even covers the reinforcement envelope substantially entirely.

[0025] According to one embodiment, the protective coating comprises at least a second protective layer formed by a layer of polyurea, polyurethane or polysilicone. Such a solution combining the first protective sleeve and a protective layer formed by a layer of polyurea, polyurethane or polysilicone makes it possible to obtain the advantages provided by a protective layer formed by a layer of polyurea, polyurethane or polysilicone while reducing the disadvantages associated therewith, i.e. by reducing the mass and volume provided by such a layer. Indeed, due to the presence of the first protective sleeve, it is possible to provide a protective layer formed by a layer of polyurea, polyurethane or polysilicone which is thinner and therefore whose weight and volume are less significant.

[0026] According to one embodiment, the second protective layer at least partially covers the first protective sleeve. According to another embodiment, the first protective sleeve is slipped at least partially onto the second protective layer. According to the embodiments, it is therefore possible to choose which of the first protective sleeve and the second protective layer covers the other depending on the properties that are desired to be provided to the protective coating.

[0027] Advantageously, the first protective layer and / or the second protective layer comprises / comprise at least one fire retardant and / or one intumescent agent. Thus, the first and / or the second protective layer confer(s) fire resistance properties. The fire retardant and / or the intumescent agent may be chosen from the group consisting of halogenated compounds, phosphorus compounds, boron compounds, metal hydroxides and metal oxides and a mixture of at least two of them. The concentration of intumescent agent in the polyurea-based layer may in particular be between 0.1% and 50% by weight, relative to the total weight of the polyurea-based layer, in particular be from 10 to 24% by weight.The halogenated intumescent agents are, in particular, chosen from chlorinated and / or brominated compounds such as polybrominated diphenyl ethers (PBDEs), tetrabrominated bisphenol A, hexabrominated cyclododecanes, decabrominated diphenylethane, Dechlorane® plus (polychlorinated flame retardant produced by OXYCHEM) and short-chain chlorinated paraffins (SCCPs). The boronated compounds are, in particular, polyborates. The phosphorus-containing compounds are, in particular, polyphosphates. The metal hydroxides are, in particular, chosen from aluminium hydroxides and magnesium hydroxides. The metal oxides are, in particular, chosen from the group comprising titanium dioxides, silica, aluminium oxides and antimony oxides. According to a method of . embodiment in which the protective coating comprises a first protective layer and a second protective layer, it is provided that the longitudinal end portions of the reinforcing envelope are covered at least in part or in whole by one protective layer not containing an intumescent agent and the other protective layer does not cover the longitudinal end portions of the reinforcing envelope.

[0028] Preferably, the first protective layer and / or the second protective layer comprises / comprise an additive selected from the group consisting of UV absorbers, light stabilizers, antioxidants, dispersing agents, wetting agents, plasticizing agents, anti-foams and impact attenuators. This improves the manufacturability and / or durability of the protective coating.

[0029] Preferably, the heat-shrinkable polymer from which the first protective sleeve and / or the second protective sleeve is made belongs to the families of polyethylenes, polyolefins, polyvinyl chlorides (PVC), polytetrafluoroethylene (PTFE), fluorocarbon polymers, polychloroprenes and fluorinated ethylene propylene (FEP). These polymers advantageously make it possible to obtain levels of shrinkage such that the diameter of the first protective sleeve shrinks by 50% to 80% compared to its original diameter when it is heated above a predetermined temperature. In addition, these heat-shrinkable polymers have the advantage of being infusible, anti-corrosion, moisture-resistant and impact-resistant. Some of these heat-shrinkable polymers also have the advantage of being transparent, which makes it possible to see the elements of the tank located under the protective sleeve.

[0030] According to one embodiment, the heat-shrinkable polymer from which the first protective sleeve is made is different from the heat-shrinkable polymer from which the second protective sleeve is made. According to another embodiment, the heat-shrinkable polymer from which the first protective sleeve is made is identical to the heat-shrinkable polymer from which the second protective sleeve is made. According to the embodiments, the heat-shrinkable polymers used to make the first protective sleeve and the second protective sleeve can therefore be chosen according to the properties that are desired to be provided to the protective coating.

[0031] According to one embodiment, the interior volume of the tank is delimited by a liner. It is then understood that the reinforcement envelope is arranged over the liner. Such an arrangement conventionally corresponds to type III tanks (when the liner is made of metal) and type IV tanks (when the liner is made of plastic). It is also understood that, if the liner is not present, the tank can be a type V tank.

[0032] According to a particular embodiment, the liner is made of plastic. It is understood that the pressurized gas tank is then a type IV tank.

[0033] According to another particular embodiment, the pressurized gas tank does not comprise a liner, the interior volume of the tank therefore not being delimited by a liner. It is understood that the pressurized gas tank is then a type V tank.

[0034] The invention also relates to a vehicle comprising a pressurized gas tank as defined above. By "vehicle" is meant any vehicle, such as a motor vehicle, a truck, a bus, a train, a construction machine or even a boat.

[0035] The invention also relates to a method for protecting a pressurized gas tank, the method comprising the following steps: (a) providing a tank comprising a reinforcing shell made of a composite material comprising reinforcing fibres and / or particles, the reinforcing shell comprising a central cylindrical part, b) slipping, onto the central cylindrical part of the reinforcement envelope, a first continuous seamless protective sleeve made with one or more heat-shrinkable polymers, c) heating the first protective sleeve so as to cause it to shrink in order to enclose the central cylindrical part of the reinforcing envelope onto which the first protective sleeve is slipped.

[0036] This method makes it possible to simply and economically install a protective coating to protect the central cylindrical part of the reinforcement envelope.

[0037] It is understood that the heating step is carried out at a temperature and for a duration allowing a retraction of the first protective sleeve in order to enclose the central cylindrical part of the reinforcement envelope.

[0038] According to one embodiment, the method further comprises the following steps: d) slipping onto the assembly obtained after step c) of heating a second continuous seamless protective sleeve made with one or more heat-shrinkable polymers, and e) heating the second protective sleeve so as to obtain a retraction of the latter in order to enclose the assembly obtained after step c).

[0039] It is thus possible to form in a simple, rapid and economical manner a protective coating formed from two protective layers having similar or different protective properties, these two protective layers being formed respectively by the first protective sleeve and the second protective sleeve.

[0040] According to one embodiment, the method further comprises a step d) consisting of applying a layer of polyurea, polyurethane or polysilicone forming a protective layer on at least part of the assembly obtained after step c). Such a solution combining the first protective sleeve and a protective layer formed by a layer of polyurea, polyurethane or polysilicone makes it possible to obtain the advantages provided by a protective layer formed by a layer of polyurea, polyurethane or polysilicone while reducing the disadvantages associated therewith, i.e. by reducing the mass and volume provided by such a layer. Indeed, due to the presence of the first protective sleeve, it is possible to provide a protective layer formed by a layer of polyurea, polyurethane or polysilicone which is thinner and therefore whose weight and volume are less significant. Brief description of the figures

[0041] The invention will be better understood on reading the following description given solely by way of example and with reference to the appended drawings in which:

[0042] [Fig.l] [Fig.l] is a schematic representation of a vehicle comprising a pressurized gas tank according to the invention;

[0043] [Fig.2] [Fig.2] is a schematic representation in longitudinal section of a pressurized gas tank according to a first embodiment of the invention, in which the protective sleeve is shown in the extended state;

[0044] [Fig.3] [Fig.3] is a schematic representation in longitudinal section of the pressurized gas tank of [Fig.3], in which the protective sleeve is shown in the shrunk state;

[0045] [Fig.4] [Fig.4] is a schematic representation in longitudinal section of a pressurized gas tank according to a second embodiment of the invention, in which the protective sleeve is shown in the shrunk state;

[0046] [Fig.5] [Fig.5] is a schematic representation in longitudinal section of a pressurized gas tank according to a third embodiment of the invention. Detailed description

[0047] Figures 1 to 5 show a motor vehicle 1 ([Fig.l]) comprising a pressurized gas tank 2 according to three embodiments of the invention. Elements that are similar between the different embodiments are designated by identical references.

[0048] First embodiment

[0049] A first embodiment of the invention is described below, with reference to Figures 1 to 3.

[0050] In the present case, the pressurized gas tank 2 is intended to store and distribute pressurized hydrogen. The pressurized gas tank 2 is therefore capable of containing pressurized hydrogen at a storage pressure of 350 bar, or even 700 bar, at ambient temperature.

[0051] The tank 2 has a generally elongated shape and has a central cylindrical section with a circular cross-section and two longitudinal ends in the shape of a dome or hemispherical shape. In the present case, the tank 2 comprises an internal envelope, also called a liner 3, a reinforcing envelope 4 and a protective coating 5.

[0052] The liner 3 is made of plastic and delimits the interior volume of the tank 2. The liner 3 has a sealing function with respect to the gas contained in the tank 2. The liner 3 is manufactured by injection or rotational molding or by extrusion-blow molding of a thermoplastic or thermosetting polymer material such as, for example, polyethylene, polyamide, polyphthalamide, polyurethane, silicone, polyoxymethylene. The plastic can be loaded with fibers, particles of nanometric or micrometric size, or even be composed of several layers. The reinforcing fibers are, for example, glass fibers, carbon fibers, basalt fibers, aramid fibers, polymer fibers, silica fibers, polyethylene fibers, natural fibers, metal fibers, metal alloy fibers or ceramic fibers.The particles can be chosen from different types of materials, such as ceramics, glass, metals, organic materials, or a combination of these. These fillers increase the deformation resistance of the composite material. In a fiber-reinforced polymer material, the reinforcing fibers and the polymer material are entangled to form a single-piece material. In addition to the reinforcing fibers, it is also possible to integrate other fillers such as reinforcing particles such as graphene particles, CSR particles (for "core-shell rubber") or carbon nanotubes.

[0053] The liner 3 is surrounded by the reinforcing envelope 4 made of composite material, which is why it is also called “composite reinforcing envelope 4”. The reinforcing envelope 4 is generally made by winding around the liner 3 strips of fibers impregnated with a resin, at different angles. The fibers used are, for example, chosen from ceramics, glasses and organic materials. For example, carbon fibers, glass fibers, aramid fibers are commonly used. The resins considered can be thermosetting, photosetting or thermoplastic. For example, for thermosetting or photosetting resins, epoxy or vinylester resins are used; and, for thermoplastic resins, polyamide or polyetheretherketone (PEEK) resins are used. The winding process can be carried out wet, with the fibers then dipping into a resin bath before being wound, or dry, with the fibers then appearing in the form of a strip of parallel fibers impregnated with resin, more commonly called "Tow preg". The resins used can be loaded with particles of nanometric and / or micrometric sizes in order to improve the properties of the composite reinforcement envelope 4. These particles can be based on a material chosen from ceramic materials, glasses, metals, organic materials or any combination thereof.For example, hollow glass beads can be used to lighten and reduce the risk of delamination of the fiber strips of the composite reinforcement envelope 4, graphene or carbon nanotubes leading to an improvement in the properties of the composite reinforcement envelope 4 from a mechanical, electrical or thermal point of view, and to a reduction in the risk of delamination of the fiber strips of the composite reinforcement envelope 4, rubber beads allowing an increase in ductility, a reduction in the risk of delamination of the fiber strips of the composite reinforcement envelope 4 as well as a reduction in residual stresses within the composite reinforcement envelope 4.

[0054] In the present case, once in place, the reinforcing envelope 4 comprises a central cylindrical part and two longitudinal ends which are substantially dome-shaped or hemispherical (Figures 2 and 3).

[0055] In order to protect the reinforcing casing 4 against environmental elements - such as high or low temperatures, water, radiation (e.g., UV), exposure to ozone, or chemical attack - the protective coating 5 is slipped over the central cylindrical portion of the reinforcing casing 4.

[0056] According to the first embodiment, the protective coating 5 comprises a first, and only, protective layer formed by a first continuous, seamless protective sleeve 6. The first protective sleeve 6 is made of one or more heat-shrinkable polymers and is configured to provide mechanical, chemical and / or fire protection.

[0057] The protective coating 5 covers in particular at least 80% of the central cylindrical part of the reinforcing casing 4, in particular at least 90%, for example at least 95%. The protective coating 5 according to the invention can cover the entire central cylindrical part of the tank.

[0058] According to the present embodiment, the heat-shrinkable polymer from which the first protective sleeve is made belongs to the families of polyethylenes, polyolefins, polyvinyl chlorides (PVC), polytetrafluoroethylene (PTFE), fluorocarbon polymers (for example, Viton®), polychloroprenes (for example, Neoprene®) and fluorinated ethylene propylene (FEP).

[0059] Advantageously, the heat-shrinkable polymer(s) are chosen such that the elastic deformation of the first protective sleeve is greater than the maximum elastic deformation of the last layer of the reinforcing envelope 4, measured under normal conditions of use. The normal conditions of use are for example defined in Regulation No. 134 of the United Nations Economic Commission for Europe (UNECE) published in the Official Journal of 17 / 05 / 2019.

[0060] The elastic deformation is measured by tensile tests according to the ISO 527 standard, over the ambient temperature range of use of the pressure vessel 2. In particular, within the framework of UNECE Regulation No. 134, these temperatures range from - 40°C to 85°C with 95% humidity. This value is compared to the maximum deformation of the upper layer of the reinforcement envelope 4, measured at the maximum working pressure (MWP). In particular, within the framework of UNECE Regulation No. 134, this maximum working pressure (MWP) corresponds to 150% of the normal working pressure (NWP).

[0061] Before being heat-shrinked, the first protective sleeve 6 has an extended diameter DI ([Fig.2]). When it is subjected to a temperature higher than a predetermined temperature, in particular when it is subjected to a temperature higher than 120°C, for example higher than 150°C, preferably around 200°C, the first protective sleeve 6 shrinks and sees its shrunk diameter D2 ([Fig.3]) reduced compared to the extended diameter DI. In the shrunk state, the first protective sleeve 6 encloses the central cylindrical part of the reinforcing jacket 4.

[0062] It may be provided that the first protective sleeve 6 comprises a fire retardant and / or an intumescent agent. Thus, the first protective sleeve 6 provides fire resistance properties.

[0063] Furthermore, it can be provided that the first protective sleeve 6 comprises an additive chosen from the group consisting of UV absorbers, light stabilizers, antioxidants, dispersing agents, wetting agents, plasticizing agents, anti-foams and impact attenuators.

[0064] A method for protecting a pressurized gas tank 2 is described below. The method comprises the following steps: a) Providing a tank 2 comprising a reinforcing envelope 4 made of composite material comprising reinforcing fibers and / or particles, the reinforcing envelope 4 comprising a central cylindrical part; b) Slipping, onto the central cylindrical part of the reinforcing casing 4, a first continuous seamless protective sleeve 6 made with one or more heat-shrinkable polymers. During this step, the first protective sleeve 6 is in its extended state and therefore has its extended diameter D1. This extended diameter D1 is chosen so as to be large enough so that the first protective sleeve 6 can be easily slipped onto the reinforcing casing 4 ([Fig.2]); c) Heating the first protective sleeve 6 so as to obtain a retraction thereof in order to enclose the central cylindrical part of the reinforcement envelope 4 onto which the first protective sleeve 6 is slipped ([Fig. 3]). The heating step is carried out at any temperature allowing heat-retraction of the first protective sleeve 6. These temperatures are generally between 120°C and 200°C. Preferably, according to the present embodiment, the heating step is carried out at 200°C. In this way, the risk of damaging the liner 3 which is made of plastic material is reduced. The means for obtaining the retraction of the first protective sleeve 6 by heating are numerous. For example, it is possible to provide, among others, pulsed hot air systems, thermal ovens, heat-retraction tunnels, infrared heaters, gas burners.

[0065] Preferably, the heating is carried out by heating from the center of the reservoir 2 towards the longitudinal ends of the reservoir 2. Thus, during the retraction of the first protective sleeve 6, which will also take place from the center of the reservoir 2 towards the longitudinal ends of the reservoir 2, the first protective sleeve 6 compresses the reinforcing envelope 4 by progressively expelling towards the longitudinal ends any air bubbles trapped in the reinforcing envelope 4 during the winding of the filaments forming the reinforcing envelope 4.

[0066] Furthermore, it is preferentially provided that the reinforcing envelope 4 has not yet undergone its annealing step when the first protective sleeve 6 is put on. In this way, not only is the evacuation of any air bubbles facilitated, but, in addition, the heating step intended to cause the retraction of the first protective sleeve 6 can also be used to carry out this annealing step of the reinforcing envelope 4. It is thus possible in a single step, and for example in a single furnace, to retract the first protective sleeve 6 and to anneal the reinforcing envelope 4. Of course, according to another method of embodiment, it is possible to anneal the reinforcement envelope 4 before inserting the first protective sleeve 6 over the central cylindrical part of the reinforcement envelope 4.

[0067] At the end of this process, the pressurized gas tank 2 obtained corresponds to a pressurized gas tank as described for the first embodiment.

[0068] According to an alternative embodiment, provision is made to introduce a suitable adhesive between the reinforcing envelope 4 and the first protective sleeve 6 in order to ensure high cohesion between these two elements.

[0069] Second embodiment

[0070] A second embodiment of the pressurized gas tank 2 according to the invention is described below with reference to [Fig. 4]. For the sake of clarity, only the elements which differ between the first and second embodiments will be presented below.

[0071] According to the second embodiment, the first protective sleeve 6 is slipped not only onto the central cylindrical part, but also onto one of the two longitudinal end parts of the reinforcing casing 4 ([Fig.4]). It is understood that it is thus possible to also protect this longitudinal end of the reinforcing casing 4 in addition to the central cylindrical part.

[0072] Alternatively, it may be provided that the first protective sleeve 6 is slipped over both the central cylindrical part and the two longitudinal end parts (not shown). This protects substantially the entire external surface of the reinforcing casing 4.

[0073] The method for protecting a pressurized gas tank 2 as described above with reference to the first embodiment is also applicable for obtaining a pressurized gas tank 2 according to the second embodiment. The only difference lies in the performance of step b). Indeed, according to the second embodiment, during step b), the first protective sleeve 6 is not only slipped onto the central cylindrical part of the reinforcing casing 4, but also onto one of the longitudinal end parts.

[0074] Third embodiment

[0075] A third embodiment of the pressurized gas tank 2 according to the invention is described below with reference to [Fig. 5]. For the sake of clarity, only the elements which differ between the first and third embodiments will be presented below.

[0076] According to the third embodiment, the protective coating 5 comprises a second protective layer ([Fig.5]).

[0077] According to a first variant of this third embodiment, the second protective layer is formed by a second continuous protective sleeve 7 seamless made with one or more heat-shrinkable polymers. In the present case, the second protective sleeve 7 is slipped onto the first protective sleeve 6 and covers it entirely ([Fig.5]). According to other embodiments, it can be provided that the second protective sleeve 7 is slipped only partially onto the first protective sleeve 6, the other part being slipped onto the reinforcing casing 4. It can also be provided that the second protective sleeve 7 is slipped only onto the first protective sleeve 6 but that it covers only part of the first protective sleeve 6.

[0078] As for the first protective sleeve 6, preferably, the second protective sleeve 7 is made of one or more heat-shrinkable polymers belonging to the families of polyethylenes, polyolefins, polyvinyl chlorides (PVC), polytetrafluoroethylene (PTFE), fluorocarbon polymers, polychloroprenes and fluorinated ethylene propylene (FEP).

[0079] Preferably, the polymer or a portion of the heat-shrinkable polymers in which the first protective layer 6 is made is different from the polymer or a portion of the heat-shrinkable polymers in which the second protective layer 7 is made.

[0080] Preferably, the thickness of the wall of the protective covering 5, that is to say in the present case the cumulative thickness of a wall of the first protective sleeve 6 and of a wall of the second protective sleeve 7, is between 0.5 and 12 mm, preferably between 0.5 and 8 mm, even more preferably between 0.5 and 3 mm.

[0081] Since the two protective sleeves 6, 7 are made of heat-shrinkable polymer, they have good adhesion properties between them. It is therefore not necessary to provide an adhesive layer between the first protective sleeve 6 and the second protective sleeve 7.

[0082] Advantageously, the heat-shrinkable polymers are chosen such that the elastic deformation of each protective sleeve 6, 7 is greater than the maximum elastic deformation of the last layer of the reinforcing envelope 4, measured under normal conditions of use. The normal conditions of use are defined in UNECE Regulation No. 134 published in the Official Journal of 17 / 05 / 2019. The elastic deformation is measured by tensile tests according to the ISO 527 standard, at temperatures from -45°C to 85°C at 95% humidity.

[0083] According to the embodiment variants, it can be provided that the first protective layer 6 and / or the second protective layer 7 comprises / comprise at least one fire retardant agent and / or one intumescent agent.

[0084] A protective layer not containing an intumescent agent in the protective coating 5 preferably has a glass transition temperature Tg, measured by dynamic mechanical analysis (sometimes called by its English acronym DMA for “dynamic mechanical analysis”), less than or equal to -40°C, in particular less than or equal to -43°C, advantageously less than or equal to -45°C.

[0085] Advantageously, a protective layer based on heat-shrinkable polymer containing an intumescent agent in the protective coating 5 preferably has a glass transition temperature Tg, measured by DMA, less than or equal to -20°C, in particular less than or equal to -30°C, advantageously less than or equal to -40°C.

[0086] Preferably, only one of the first protective sleeve 6 and the second protective sleeve 7 comprises an intumescent agent and provides fire resistance properties to the protective coating 5. The protective sleeve which does not comprise an intumescent agent then provides impact resistance to the protective coating 5. The first and second protective sleeves 6, 7 contribute to the resistance to corrosion and chemical attack of the protective coating 5.

[0087] Similarly, according to the embodiments, it can be provided that the first protective layer 6 and / or the second protective layer 7 comprises / comprise an additive chosen from the group consisting of UV absorbers, light stabilizers, antioxidants, dispersing agents, wetting agents, plasticizing agents, anti-foams and impact attenuators.

[0088] Preferably, it is provided that the protective layer in direct contact with the reinforcing envelope 4 - that is to say the first protective sleeve 6 in the present case - has impact resistance properties. The other protective layer - that is to say the second protective sleeve 7 in the present case - preferably has both intumescent properties and properties of resistance to chemical attack and mechanical stress.

[0089] The method for protecting a pressurized gas tank 2 as described above with reference to the first embodiment is also applicable for obtaining a pressurized gas tank 2 according to this variant of the third embodiment. It differs therefrom only in that it further comprises the following steps: d) slipping the second protective sleeve 7 onto the assembly obtained after step c) of heating, and e) heating the second protective sleeve 7 so as to obtain a retraction thereof in order to enclose the assembly obtained after step c).

[0090] According to a second variant of the third embodiment, the second protective layer of the protective coating 5 is formed by a layer of polyurea 8, polyurethane or polysilicone.

[0091] Preferably, according to this variant of the third embodiment, the first protective sleeve 6 is covered by the second protective layer, for example, a layer of polyurea.

[0092] The use of aliphatic polyisocyanates for the production of the second protective layer based on polyurea is preferred when seeking to prepare a product which does not yellow or which has a color suitable for compliance with certain standards, in particular when the second protective layer forms the outer layer of the protective coating 5.

[0093] Advantageously, at least one of the two protective layers of the protective coating 5 contains at least one additive chosen from UV absorbers, light stabilizers, antioxidants, dispersing agents, wetting agents such as surfactants, plasticizing agents, anti-foams and impact attenuators, also called impact modifiers. Advantageously, this protective layer comprises an additive, chosen from surfactants, which can fulfill a function of wetting agent and suspension stabilizer.

[0094] Advantageously, the second protective layer based on polyurea 8 contains an intumescent agent chosen from the group consisting of halogenated compounds, phosphorus compounds, boron compounds, metal hydroxides and metal oxides and a mixture of at least two of them. The halogenated intumescent agents are, in particular, chosen from chlorinated and / or brominated compounds such as polybromo-diphenyl ethers (PBDE), tetrabromo-bisphen ol A, hexabromo-cyclododecanes, decabromo-diphenylethane, dechlorane plus and short-chain chlorinated paraffins (SCCP). The boron compounds are, in particular, polyborates. The phosphorus compounds are, in particular, polyphosphates. The metal hydroxides are, in particular, chosen from aluminum hydroxides and magnesium hydroxides.The metal oxides are, in particular, chosen from the group comprising titanium dioxides, silica, aluminum oxides and antimony oxides.

[0095] Preferably, when the second polyurea-based protective layer 8 comprises an intumescent agent, the polyurea is essentially aliphatic. The polyurea is then preferably prepared from short-chain aliphatic or aromatic amines. In addition, it preferably contains at least one compound chosen from diammonium decaborate, hexane 6-olide and C18 unsaturated fatty acids.

[0096] The second polyurea-based protective layer 8 can be applied or deposited on the assembly obtained after step c) of the method for protecting a tank 2 as described for the first embodiment. The application or deposit can be carried out according to methods known to those skilled in the art.

[0097] It can in particular be deposited by spraying under pressure, by immersion or by brush. Preferably, the second protective layer based on polyurea 8 is applied by spraying.

[0098] The steps of depositing the second protective layer based on polyurea 8 are carried out at a temperature of 15°C to 75°C. They can therefore be carried out at room temperature, this temperature preferably having to be greater than or equal to the dew point +3°C.

[0099] It can be provided that the steps of depositing the second protective layer based on polyurea 8 are carried out at room temperature. For this, the hollow body obtained after leaving the oven, that is to say at the end of step c) of the protection method, is left to rest for a variable period, until cooling. The time to obtain a protective coating 5 comprising a second protective layer based on polyurea 8 is less than or equal to twenty-four hours, in particular less than or equal to seven hours, generally between three hours and seven hours.

[0100] The second protective layer based on polyurea 8 can be prepared by any means known to those skilled in the art. For example, a resin mixture as defined above is prepared, preferably comprising amines with short aliphatic or aromatic chains and containing an intumescent agent. A hardener is also prepared, comprising, for example, a mixture of polyisocyanate compounds.

[0101] The mixture of resin and hardener is introduced into a mixing chamber of a spraying device, in a ratio of 1:1 + / -3%. The reaction is almost immediate and the polyurea is sprayed onto at least part of the assembly resulting from step c) of the method for protecting the tank 2 and forms the second polyurea-based protective layer 8. The spraying conditions and the quantity of mixture are adjusted to obtain an intumescent layer having a protective layer with a thickness greater than or equal to 1 mm, and less than or equal to 3 mm, in particular less than or equal to 2 mm.

[0102] Advantageously, the temperature in the mixing chamber is 80°C + / - 10°C, and the pressure is 180 bars + / - 20 bars.

[0103] The resin and hardener mixtures are sprayed onto the assembly resulting from step c) of the method for protecting the tank 2 by a spray gun, known to those skilled in the art. For example, a so-called "airless" gun with a mechanical chamber and a flat jet is used.

[0104] The polyurea layer is then left to crosslink for a time of between three and seven hours, at room temperature or in an enclosure maintained at a temperature of approximately 70°C in order to form the second protective layer based on polyurea 8.

[0105] According to an advantageous embodiment of the invention, the polyurea mixture POLYRESYST® H 20020-70 RE and POLYRESYST® H20020-70 HA marketed by Huntsman is used for mechanical resistance.

[0106] According to another advantageous embodiment, the polyurea mixture POLYRESYST H24505-90W HA and POLYRESYST H24505-90W RE or POLYRESYST H24505-57 HA and POLYRESYST H24505-57 RE marketed by Huntsman is used for fire resistance.

[0107] The thickness of the protective coating 5 is adapted by a person skilled in the art according to the desired properties. Preferably, the total thickness of the protective coating, comprising the thickness of a wall of the first protective sleeve 6 and the thickness of the second polyurea-based protective layer 8, is between 0.5 and 12 mm, preferably between 0.5 and 8 mm, even more preferably between 0.5 and 3 mm.

[0108] Advantageously, the superposition of the first protective sleeve 6 and the second polyurea-based protective layer 8 is chosen such that the elastic deformation of the protective coating 5 is greater than the maximum elastic deformation of the last layer of the reinforcing envelope 4, measured under normal conditions of use. The normal conditions of use are defined in UNECE Regulation No. 134 published in the Official Journal of 17 / 05 / 2019. The elastic deformation is measured by tensile tests according to ISO 527, at temperatures from -45°C to 85°C at 95% humidity.

[0109] Regardless of the embodiment described above, the protective coating 5 protects the tank at temperatures from -40°C to +85°C, it can withstand impacts of 30 Joules at -40°C and provides resistance to chemical and environmental agents (UV, corrosion). It also provides fire resistance by delaying fire through its intumescent properties when an intumescent agent is present.

[0110] The invention is not limited to the embodiments presented in the detailed description and other embodiments will become clear to those skilled in the art. List of references [YES] 1: motor vehicle 2: pressurized gas tank 3: liner 4: reinforcement envelope 5: protective coating 6: first protective sleeve 7: second protective sleeve 8: polyurea layer DI: diameter of the first protective sleeve in the extended state D2: diameter of the first protective sleeve in the shrunk state

Claims

Claims

1. A pressurized gas tank (2) defining an interior volume for storing a pressurized gas and comprising: - a reinforcing envelope (4) made of a composite material comprising reinforcing fibers and / or particles, the reinforcing envelope (4) comprising a central cylindrical portion, characterized in that it further comprises: - a protective covering (5) slipped onto the central cylindrical portion of the reinforcing envelope (4), the protective covering (5) comprising at least a first protective layer formed by a first continuous seamless protective sleeve (6), the first protective sleeve (6) being made with one or more heat-shrinkable polymers, the protective covering (5) being configured to provide mechanical, chemical and / or fire protection.

2. A pressurized gas tank (2) according to claim 1, wherein the protective coating (5) comprises at least a second protective layer formed by a second continuous seamless protective sleeve (7) made with one or more heat-shrinkable polymers.

3. A pressurized gas tank (2) according to claim 2, wherein the second protective sleeve (7) is slipped at least partly over the first protective sleeve (6).

4. A pressurized gas tank (2) according to any preceding claim, wherein the central cylindrical portion of the reinforcing jacket (4) is arranged between two longitudinal end portions of the reinforcing jacket (4), and wherein the protective covering (5) is further slipped over at least one of the two longitudinal end portions of the reinforcing jacket (4).

5. A pressurized gas tank (2) according to claim 1, wherein the protective coating (5) comprises at least one second protective layer formed by a layer of polyurea (8), polyurethane or polysilicon.

6. A pressurized gas tank (2) according to any preceding claim, wherein the first protective layer and / or the second protective layer comprises / include at least one fire retardant and / or intumescent agent.

7. A pressurized gas tank (2) according to any preceding claim, wherein the first protective layer and / or the second protective layer comprises an additive selected from the group consisting of UV absorbers, light stabilizers, antioxidants, dispersing agents, wetting agents, plasticizing agents, antifoams and impact attenuators.

8. A pressurized gas tank (2) according to any one of the preceding claims, wherein the heat-shrinkable polymer from which the first protective sleeve (6) and / or the second protective sleeve (7) is made belongs to the families of polyethylenes, polyolefins, polyvinyl chlorides (PVC), polytetrafluoroethylene (PTFE), fluorocarbon polymers, polychloroprenes and fluorinated ethylene propylene (FEP).

9. A pressurized gas tank (2) according to any one of the preceding claims, wherein the interior volume of the tank (2) is delimited by a liner (3), preferably the liner (3) is made of plastic.

10. Vehicle (1) comprising a pressurized gas tank (2) according to any one of the preceding claims.

11. Method for protecting a pressurized gas tank (2), the method comprising the following steps: a) providing a tank (2) comprising a reinforcing jacket (4) made of a composite material comprising reinforcing fibers and / or particles, the reinforcing jacket (4) comprising a central cylindrical part, b) slipping, onto the central cylindrical part of the reinforcing jacket (4), a first continuous seamless protective sleeve (6) made with one or more heat-shrinkable polymers, c) heating the first protective sleeve (6) so as to obtain a retraction thereof in order to enclose the central cylindrical part of the reinforcing jacket (4) onto which the first protective sleeve (6) is slipped.

12. A method of protecting a pressurized gas tank (2) according to claim 11, further comprising the following steps: d) slipping onto the assembly obtained after heating step c) a second continuous seamless protective sleeve (7) made with one or more heat-shrinkable polymers, and e) heating the second protective sleeve (7) so as to obtain a retraction thereof in order to enclose the assembly obtained after step c).

13. Method for protecting a pressurized gas tank (2) according to claim 11, further comprising a step d) consisting of applying a layer of polyurea (8), polyurethane or polysilicone forming a protective layer on at least part of the assembly obtained after step c).

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