Hydrogen pipe

Abstract

A tube and its use for guiding hydrogen, preferably in a vehicle. The tube surrounds a tube lumen and comprises a plurality of layers, wherein the tube layers comprise at least two barrier layers. The inner barrier layer comprises a first plastic, and the outer barrier layer comprises a second plastic. The first plastic is vinyl alcohol plastic, and the second plastic is vinyl alcohol plastic. The barrier layers are separated from each other by a separator layer, and the tube comprises a support layer, which is surrounded by the inner barrier layer.

Description

Technical Field

[0001] The invention relates to the use of a tube according to the preamble of claim 1 for conducting hydrogen. Background Art

[0002] US 2004 / 0069361 A1 discloses such a tube for conducting hydrogen. The tube comprises an outer barrier layer composed of ethylene-vinyl alcohol copolymer (EVOH, also commonly referred to as "EVAL"), which is surrounded by two adhesive layers composed of polyurethane. The innermost layer comprises a fluoropolymer, particularly polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene-hexafluoropropylene fluoride terpolymer (EFEP), or ethylene-tetrafluoroethylene copolymer (ETFE), and due to its excellent barrier effect, this innermost layer simultaneously forms an inner barrier layer. The outermost layer of the tube is formed of polybutylene terephthalate (PBT), which abuts the outer side of the outer barrier layer and thus constitutes a boundary layer.

[0003] A tube for conducting hydrogen is also disclosed in US 2010 / 0035116 A1. This tube has a barrier layer composed of EVOH, which is surrounded by a boundary layer composed of polyamide (PA). The outermost layer comprises polyphthalamide (PPA) and lies directly on the boundary layer. The barrier layer composed of EVOH surrounds a directly adjacent layer composed of ETFE, which in turn is bounded by an innermost layer composed of PA.

[0004] A disadvantage of these known hydrogen tubes is that the permeability is still too high, so that too much hydrogen diffuses through the tube and is thus lost, which is particularly noticeable when the vehicle is parked for a long time. Summary of the Invention

[0005] This object is achieved by a tube, in particular by using a tube for conducting hydrogen, in particular for use in vehicles, wherein the tube surrounds a tube cavity and comprises a plurality of layers, wherein the tube has at least two barrier layers, wherein the inner barrier layer of at least two barrier layers comprises a first plastic, wherein the outer barrier layer of at least two barrier layers comprises a second plastic, wherein the first plastic is a vinyl alcohol plastic, wherein the barrier layers are separated from one another by separating layers, wherein the tube has a support layer, wherein the support layer is surrounded by the inner barrier layer, wherein the second plastic is a vinyl alcohol plastic.

[0006] The present invention is primarily based on the recognition that when using vinyl alcohol plastic, the barrier layer has a very low permeability to hydrogen. This permeability can be significantly reduced by increasing the barrier layer thickness. However, barrier layers made of vinyl alcohol plastic are quite brittle, which is critical for pipes that are typically subjected to multiple bending. It has been found that barrier layers with excessively thick layers develop microcracks significantly more frequently during bending. These microcracks lead to significantly higher permeability, so that increasing the thickness of the vinyl alcohol barrier layer only constitutes a very limited means of improving the barrier properties.

[0007] In particular, the present invention is based on the recognition that providing a second barrier layer made of vinyl alcohol plastic with a separator layer interposed between the two barrier layers allows the total layer thickness of the barrier layer made of vinyl alcohol plastic to be significantly greater, while the probability of cracking remains consistently low. By providing two, three, or more vinyl alcohol barrier layers with a corresponding number of interposed separator layers, the total layer thickness of the combined layer thicknesses of the individual vinyl alcohol barrier layers can even be doubled compared to a single vinyl alcohol barrier layer, while the probability of cracking, and therefore the scrap rate, remains at a constantly low level. The object mentioned at the outset is thereby achieved.

[0008] The term "layer" preferably means that one layer is distinguishable from another layer because the two layers have different material compositions. A layer does not necessarily have to consist of a single, unitary, or uniformly distributed material composition. A layer may have multiple sub-layers or plies that are themselves distinguishable from each other. A single layer advantageously consists of a single, uniformly distributed material composition.

[0009] The term "vinyl alcohol plastic" preferably refers to polymers containing vinyl alcohol monomers, and in particular refers to ethylene-vinyl alcohol copolymers (EVOH), polyvinyl alcohol (PVOH), and butene glycol-vinyl alcohol copolymers (BVOH). Vinyl alcohol plastic can be the only plastic of the inner and / or outer barrier layer. According to one embodiment, the inner and / or outer barrier layer comprises a mixture of vinyl alcohol plastic and a second material or an additional material, and in particular a mixture with a plastic or an additional plastic.

[0010] It is very particularly preferred that the tube is a plastic tube and preferably contains at least 50% by weight, 70% by weight, 90% by weight, 95% by weight, or 97% by weight of plastic. It is preferred that the protective layer and / or the supporting layer and / or the inner barrier layer and / or the separating layer and / or the outer barrier layer and / or the boundary layer contain at least 50% by weight, 70% by weight, 90% by weight, or 95% by weight of plastic, in particular a thermoplastic. The tube advantageously has at least one bend, preferably at least two, three, four, or five bends. The tube advantageously has an outer diameter of at least 2 mm, 3 mm, or 4 mm.

[0011] It is particularly preferred that the separator layer comprises a plastic, preferably polyamide, and in particular PA 6. When the separator layer comprises polyamide, it provides good toughness, resulting in the more brittle barrier layers being separated from one another by a very strong, somewhat softer material. It is very particularly preferred that the separator layer comprises a softer material than the inner and / or outer barrier layers. The term "softer" preferably relates to the Shore D hardness measured at room temperature and, in particular, to the standard DIN EN ISO 868:2003-10. The separator layer creates two thinner barrier layers, so that the layer composite consisting of the inner, separator, and outer barrier layers as a whole is less brittle. When the separator layer comprises PA 6, the separator layer is not only very strong but also adheres well to the inner and outer barrier layers. As a result, the layer composite consisting of the inner, separator, and outer barrier layers has little tendency to delaminate. The separator layer advantageously adjoins the inner and / or outer barrier layers. The layer thickness of the separator layer is advantageously at least 0.05 mm, 0.06 mm, or 0.08 mm. The layer thickness of the separating layer preferably amounts to at most 0.3 mm, 0.4 mm, or 0.5 mm. A greater layer thickness of the separating layer generally has the advantage of separating the barrier layers further from one another, thereby enabling even stronger bending. Conversely, when the tube is to be designed to be as light or small as possible, the thinnest possible layers are advantageous, which also saves on material.

[0012] It is highly preferred that the support layer be made of a softer material than the inner barrier layer. Advantageously, the support layer adjoins the inner barrier layer. The support layer advantageously comprises a plastic, preferably a polyamide, and in particular PA 6. When the support layer comprises a softer material than the inner barrier layer or polyamide, it stabilizes the inner side of the inner barrier layer and thereby, in particular, reduces the probability of crack formation on the inner side of the inner barrier layer. When the support layer comprises PA 6, this provides the support layer with the advantages of a polyamide material and improved adhesion to the inner side of the inner barrier layer, which reduces the probability of delamination during bending. The support layer may be the innermost layer and preferably contains an additive to increase electrical conductivity. For example, the additive may be conductive carbon black. The support layer may have a thickness of at least 0.05 mm, 0.06 mm, or 0.07 mm. Advantageously, the support layer has a thickness of at most 0.5 mm, 0.4 mm, or 0.3 mm. It is highly preferred that the support layer have a thickness less than that of the separator layer. This is because, unlike the separator layer, the support layer does not need to separate any barrier layers from one another, so a smaller thickness is generally sufficient. The layer thickness of the support layer can preferably be at least 5% or 10% or 20% or 30% or 50% smaller than the layer thickness of the separation layer.

[0013] According to particularly preferred embodiments, the first and / or second plastic is EVOH, BVOH, or PVOH, with EVOH or PVOH being preferred. These three plastic types are particularly preferred because they each have good barrier properties, are easy to process, and, as a whole, require relatively low production costs. Because BVOH can be made significantly softer than EVOH and PVOH and is less advantageous than EVOH and PVOH in terms of producing specific hurdles, EVOH and PVOH are primarily considered in the present invention. The vinyl alcohol plastic EVOH is particularly preferred. The barrier properties of EVOH are controlled, in particular, by its ethylene content. The lower the ethylene content, the better the barrier effect and the more brittle the EVOH. Therefore, tubes containing a small amount of ethylene in the EVOH particularly benefit from the present invention. The ethylene content of the EVOH in the inner and / or outer barrier layer is preferably at most 45%, 40%, 36%, or 33%. It is preferred that the inner and outer barrier layers have the same material composition. The inner and outer barrier layers may have different material compositions.

[0014] According to a particularly preferred embodiment, the thickness of the inner barrier layer is less than or equal to (≤) the thickness of the outer barrier layer, and preferably less than the thickness of the outer barrier layer. This results in a reduced probability of cracking while maintaining the combined thickness of the two barrier layers. This is because, in the event of strong bending, the inner barrier layer is subject to greater loads than the outer barrier layer, so the outer barrier layer can have a slightly greater thickness than the inner barrier layer. Preferably, the thickness of the inner barrier layer is at least 5%, 10%, or 15% less than the thickness of the outer barrier layer. The thickness of the inner barrier layer is preferably at most 70%, 60%, or 50% less than the thickness of the outer barrier layer. The thickness of the inner barrier layer can preferably be at least 0.05 mm, 0.06 mm, or 0.08 mm. The thickness of the inner barrier layer is advantageously at most 0.5 mm, 0.4 mm, or 0.3 mm. The thickness of the outer barrier layer is preferably at least 0.06 mm, 0.07 mm, or 0.09 mm. The thickness of the outer barrier layer is preferably at most 0.6 mm, 0.5 mm, or 0.4 mm.

[0015] The combined thickness of the inner and outer barrier layers is preferably at least 0.11 mm, 0.12 mm, or 0.13 mm. Preferably, the combined thickness of the inner and outer barrier layers is at most 1.0 mm, 0.8 mm, 0.6 mm, or 0.4 mm. The combined thickness of the inner and outer barrier layers is advantageously at least 7%, 14%, or 20% of the total wall thickness of the tube. The combined thickness of the inner and outer barrier layers is preferably at most 60%, 50%, or 40% of the total wall thickness of the tube. The total wall thickness of the tube may be at least 0.5 mm, 0.8 mm, or 1.0 mm. The total wall thickness of the tube advantageously is at most 4.0 mm, 3.5 mm, or 3.0 mm.

[0016] The tube may comprise a third barrier layer and a second separator layer, wherein the third barrier layer surrounds the outer barrier layer, wherein the second separator layer is arranged between the outer barrier layer and the third barrier layer. Preferably, the third barrier layer comprises a plastic, wherein the plastic is preferably a vinyl alcohol plastic. The vinyl alcohol plastic of the third barrier layer may be EVOH, PVOH or BVOH, wherein EVOH or PVOH is preferred. The plastic of the third barrier layer is particularly preferably EVOH. The EVOH of the third barrier layer preferably has an ethylene content of at least 45%, 40%, 36% or 33%. The third barrier layer advantageously has the same material composition as the inner barrier layer and / or the outer barrier layer. The advantage of the third barrier layer is that the risk of cracking is further reduced by means of the second separator layer while the combined layer thickness of the three barrier layers remains constant.

[0017] The second separator layer preferably comprises a plastic, particularly polyamide, preferably PA6. Advantageously, the material of the second separator layer is softer than the material of the outer barrier layer and / or the third barrier layer. This stabilizes the inner side of the third barrier layer and the outer side of the outer barrier layer. In the case of polyamide, the separator layer has good mechanical properties, and in the case of PA6, these good mechanical properties are also maintained through good adhesion. The second separator layer advantageously adjoins the outer barrier layer and / or the third barrier layer.

[0018] The thickness of the second separator layer is advantageously less than the thickness of the boundary layer. Preferably, the thickness of the second separator layer is greater than the thickness of the support layer. The separator layer may have a thickness of at least 0.05 mm, 0.06 mm, or 0.07 mm. The thickness of the second separator layer advantageously reaches a maximum of 0.5 mm, 0.4 mm, or 0.3 mm.

[0019] It is preferred that the third barrier layer has a greater thickness than the first and / or second barrier layers. This is possible because the third barrier layer is subject to lower forces than the inner and outer barrier layers when the tube is bent. The third barrier layer can have a thickness of at least 0.07 mm, 0.08 mm, or 0.1 mm. Advantageously, the third barrier layer has a thickness of at most 0.7 mm, 0.6 mm, or 0.5 mm.

[0020] According to a preferred embodiment, the boundary layer surrounds the outer barrier layer or the third barrier layer, wherein the boundary layer preferably adjoins the outer barrier layer or the third barrier layer. The boundary layer advantageously comprises a plastic, preferably a polyamide and / or a thermoplastic elastomer, and particularly preferably PA 6, PA 11, PA 12, and / or PA 612. It is preferred that the boundary layer is thicker than the supporting layer and / or thicker than the separating layer. A thick boundary layer is advantageous because it protects the tube from external influences. In addition to chemical loads, these primarily include mechanical loads, to which a brittle, unprotected barrier layer can react sensitively. The layer thickness of the boundary layer can be at least 0.07 mm, 0.08 mm, or 0.09 mm. The layer thickness of the boundary layer preferably reaches a maximum of 0.4 mm, 0.3 mm, or 0.2 mm. According to an embodiment, the boundary layer comprises only one sheet, wherein the single sheet preferably comprises a plastic, more preferably a polyamide and / or a thermoplastic elastomer, in particular PA 6, PA 11, PA 12, and / or PA 612. The plastic may contain additives that improve the adhesion of the single sheet of the boundary layer to the vinyl plastic. It is very preferred that the material of the single sheet of the boundary layer is softer than the material of the outer barrier layer and / or the third barrier layer. This stabilizes the outer side of the outer barrier layer or the third barrier layer.

[0021] The pipe preferably comprises at least one adhesive lamella. According to one embodiment, the boundary layer has an adhesive lamella and a boundary lamella, wherein the boundary lamella preferably surrounds the adhesive lamella. Advantageously, the outer boundary lamella comprises plastics, preferably comprises polyamide and / or thermoplastic elastomer, particularly PA 6, PA 11, PA 12 and / or PA612. The adhesive lamella is advantageously arranged between the outer barrier layer or the third barrier layer and the boundary lamella. The adhesive layer advantageously abuts the outer barrier layer or the third barrier layer. The adhesive lamella preferably abuts the boundary lamella. This arrangement makes it possible to also arrange other plastics that are not too good at adhering to vinyl alcohol plastic, so as to reduce the probability of delamination. The example of the not too good plastics that adheres comprises PA 11, PA 12 or PA 612, and this not too good plastics that adheres can be arranged on the outer barrier layer or the third barrier layer by means of adhesive, which for example comprises polyolefin, and particularly polypropylene or polyethylene.

[0022] The support layer may surround the protective layer, wherein the protective layer preferably forms the innermost layer of the tube. The protective layer preferably comprises plastic and may, in particular, comprise a fluoropolymer or polyamide. For example, the fluoropolymer may be ETFE. The protective layer may have a layer thickness of at least 0.05 mm, 0.07 mm, or 0.09 mm. Advantageously, the protective layer has a layer thickness of at most 0.3 mm, 0.25 mm, or 0.2 mm.

[0023] The innermost layer, in particular the supporting layer or the protective layer, advantageously contains an additive for improving the electrical conductivity. For example, the additive may be conductive carbon black. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention is described below based on three exemplary embodiments through three figures.

[0025] Figure 1 shows a cross section of a first tube according to the invention,

[0026] Figure 2 shows a cross section of a second tube according to the invention, and

[0027] Figure 3 A third tube according to the invention is shown in cross section. DETAILED DESCRIPTION

[0028] Figure 1 A cross section of a first exemplary embodiment of a tube 1 is shown. Figure 1 The tube 1 of this exemplary embodiment includes a total of five layers (3, 4, 5, 6, 7), which surround the lumen 2. From the inside out, the tube 1 of this exemplary embodiment includes a support layer 3, an inner barrier layer 4, a separator layer 5, an outer barrier layer 6, and a boundary layer 7.

[0029] The inner barrier layer 4 and the outer barrier layer 6 are each composed of vinyl alcohol plastic. In this exemplary embodiment, both barrier layers comprise EVOH, with the inner barrier layer 4 and / or the outer barrier layer 6 preferably consisting of EVOH. The ethylene content of the vinyl alcohol plastic of the inner barrier layer 4 and / or the outer barrier layer 6 preferably reaches up to 35 mol%, and more preferably up to 33 mol%. According to a specific embodiment, the ethylene content of the inner barrier layer 4 and / or the outer barrier layer 6 reaches up to 32 mol%. It is preferred that the inner barrier layer 4 and / or the outer barrier layer 6 consist of vinyl alcohol plastic. The inner barrier layer 4 and the outer barrier layer 6 advantageously consist of the same material. In this exemplary embodiment, for example, the inner barrier layer 4 may have a layer thickness of 0.12 mm, while the outer barrier layer 6 may have a layer thickness of 0.15 mm.

[0030] It is highly preferred that the separator layer 5 comprises a plastic, preferably polyamide, and particularly preferably PA6. PA6 adheres well to vinyl alcohol plastics, and in particular to ethylene-vinyl alcohol copolymers, so that the separator layer 5, together with the two barrier layers 4, 6, forms a strong layer composite 4, 5, 6. Furthermore, polyamide or PA6 is less brittle or more resilient than the two barrier layers 4, 6 composed of EVOH, so from this perspective the separator layer also stabilizes the layer composite 4, 5, 6. The basic concept of the present invention becomes clear from the layer composite 4, 5, 6, because the separator layer 5 allows for significantly better bending than a continuous barrier layer having a layer thickness corresponding to 0.27 mm, and thus corresponding to the combined layer thickness of the inner barrier layer 4 and the outer barrier layer 6. In this exemplary embodiment, the separator layer 5 can have a layer thickness of 0.1 mm.

[0031] The protective layer 3 preferably comprises, and preferably consists of, a plastic. In particular, the plastic of the support layer 3 can include polyamide, preferably PA 6. A typical layer thickness of the support layer can be 0.08 mm. In this exemplary embodiment, the support layer 3 is the layer that delimits the tube 1 toward the inside, and thus toward the lumen 2, and is therefore also in contact with the hydrogen gas. In this regard, the support layer protects, for example, the inner barrier layer 4 from erosion. However, the support layer 3 specifically supports the relatively brittle inner barrier layer 4 on its inner side, thereby reducing cracking during bend formation. Furthermore, the support layer 3 protects the inner barrier layer 4 when the tube 1 is pushed onto the quick connector and subjected to a press fit therein. When the support layer 3 forms the innermost layer of the tube 1, it advantageously contains an additive that increases electrical conductivity. For example, this additive can be conductive carbon black, which makes the support layer 3, as the innermost layer, conductive enough to avoid critical charge levels.

[0032] It is preferred that the tube 1 has a boundary layer 7, which in the figure forms the outermost layer of the tube 1. In this exemplary embodiment, the boundary layer 7 is arranged directly on the outer barrier layer 6. The boundary layer 7 advantageously consists of plastic or polyamide or PA 6. The layer thickness of the boundary layer 7 can be up to 0.3 mm.

[0033] Figure 2 The exemplary embodiment shown is a tube 1 which is constructed identically to the first exemplary embodiment with regard to layers 3 to 6. However, in contrast to the first exemplary embodiment, the boundary layer is designed as a double layer. Figure 2The boundary layer 7 of the second exemplary embodiment comprises an adhesive layer 8 and a boundary layer 9. The boundary layer 9 of this exemplary embodiment is preferably composed of plastic, in particular polyamide, and particularly preferably PA 11 or PA 12. Due to the poor adhesion of PA 11 or PA 12 to vinyl alcohol plastics, an adhesive layer 8 is provided, which can, for example, comprise a polyolefin, in particular polypropylene or polyethylene. However, the adhesive layer can also comprise an adhesion-modified polyamide or polyamide 6. In this exemplary embodiment, the layer thickness of the adhesive layer 8 can be 0.05 mm. For example, the layer thickness of the boundary layer 9 can reach 0.25 mm.

[0034] Figure 3 A third exemplary embodiment of a tube 1 according to the invention is shown, which tube 1 is connected to Figure 2 The exemplary embodiment shown in FIG. 1 differs primarily in that, instead of the support layer 3 forming the innermost layer of the tube 1 , the protective layer 10, which adjoins the support layer 3 internally, forms the innermost layer of the tube 1 . For example, the protective layer 10 may comprise a polyamide or a fluoropolymer. The fluoropolymer is preferably ETFE. The protective layer 10 may have a thickness of 0.15 mm. The protective layer 10 advantageously contains an additive to increase its electrical conductivity. In particular, the additive may be conductive carbon black.

[0035] Reference Signs List

[0036] 1 tube

[0037] 2 Lumen

[0038] 3 Support layer

[0039] 4 Inner barrier layer

[0040] 5 separation layers

[0041] 6 Outer barrier layer

[0042] 7 Boundary layer

[0043] 8 7 adhesive sheet

[0044] 9 7 boundary slice

[0045] 10 protective layer

Claims

1. Use of a tube (1) for guiding hydrogen, wherein the tube (1) surrounds a tube cavity (2) and comprises a plurality of layers, wherein the tube (1) has at least two barrier layers, wherein the inner barrier layer (4) of the at least two barrier layers comprises a first plastic, wherein the outer barrier layer (6) of the at least two barrier layers comprises a second plastic, wherein the first plastic is vinyl alcohol plastic, the layer thickness of the inner barrier layer is smaller than the layer thickness of the outer barrier layer, wherein the barrier layers are separated from one another by a separator layer (5), which is formed from a softer material than the barrier layers, the separator layer comprising polyamide, wherein the tube (1) has a support layer (3), wherein the support layer (3) is surrounded by the inner barrier layer (4), and wherein the second plastic is vinyl alcohol plastic.

2. The use according to claim 1, wherein The use described is use in a vehicle.

3. The use according to claim 1, wherein The polyamide of the separation layer (5) comprises PA 6.

4. The method according to claim 1, wherein The support layer (3) comprises a material that is softer than the material of the inner barrier layer (4).

5. The method according to claim 1, wherein The first plastic and / or the second plastic is ethylene vinyl alcohol copolymer (EVOH), butene glycol vinyl alcohol copolymer (BVOH) or polyvinyl alcohol (PVOH).

6. The method according to claim 1, wherein The layer thickness of the inner barrier layer (4) is less than or equal to the layer thickness of the outer barrier layer (6).

7. The method according to claim 1, wherein The added thickness of the layer thicknesses of the inner barrier layer (4) and the outer barrier layer (6) is at least 0.1 mm or 0.2 mm or 0.3 mm.

8. The use according to claim 1, wherein The tube (1) has a third barrier layer and a second separating layer, wherein the third barrier layer surrounds the outer barrier layer (6), wherein the second separating layer is arranged between the outer barrier layer (6) and the third barrier layer.

9. The use according to claim 8, wherein A boundary layer (7) surrounds the outer barrier layer (6) or the third barrier layer.

10. The use according to claim 9, wherein The boundary layer (7) comprises plastic.

11. The use according to claim 9, wherein The boundary layer (7) comprises polyamide.

12. The use according to claim 9, wherein The boundary layer (7) comprises PA 6, PA 11, PA 12 and / or PA 612.

13. The use according to claim 9, wherein The tube (1) has at least one adhesive ply (8), wherein the boundary layer (7) comprises the adhesive ply (8) and a boundary ply (9).

14. The use according to claim 13, wherein The boundary layer (9) comprises plastic.

15. The use according to claim 13, wherein The boundary layer (9) comprises polyamide.

16. The use according to claim 13, wherein The boundary layer (9) comprises PA 11, PA 12 and / or PA612.

17. The use according to one of claims 1 to 3, wherein The support layer (3) surrounds a protective layer (10), wherein the protective layer (10) forms the innermost layer of the tube (1).

18. The use according to claim 17, wherein The protective layer (10) comprises a fluorine-containing polymer.

19. The use according to claim 17, wherein The protective layer (10) comprises ETFE.

20. The use according to one of claims 1 to 3, wherein The innermost layer of the tube (1) contains an additive for improving electrical conductivity.

21. The use according to claim 20, wherein The innermost layer of the tube (1) contains conductive carbon black.

22. The use according to claim 20, wherein The innermost layer of the tube (1) is the supporting layer (3) or the protective layer (10).

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