HYDROGEN PIPE

Description

[0001] The invention relates to the use of a pipe for conducting hydrogen according to the preamble of claim 1. Automotive pipelines for fuels produced by coextrusion are known from EP1182345.

[0002] Such a pipe for conducting hydrogen is disclosed in US 2004 / 0069361 A1. This pipe comprises an outer barrier layer made of ethylene-vinyl alcohol copolymer (EVOH, often referred to as "EVAL"), which is surrounded by two polyurethane adhesion promoter layers. The innermost layer comprises a fluoropolymer, in particular polyvinylidene difluoride (PVDF), ethylene-tetrafluoroethylene-hexafluoropropylene fluoro terpolymer (EFEP), or ethylene-tetrafluoroethylene copolymer (ETFE), and simultaneously forms an inner barrier layer due to its good barrier effect. The outermost layer of this pipe is formed by polybutylene terephthalate (PBT), lies against an outer side of the outer barrier layer, and therefore represents a boundary layer.

[0003] A pipe for conducting hydrogen is further disclosed in US 2010 / 0035116 A1. This pipe has a barrier layer made of EVOH, which is enclosed by a boundary layer made of polyamide (PA). An outermost layer comprises a polyphthalamide (PPA) and lies directly on the boundary layer. The EVOH barrier layer encloses a directly adjacent layer comprising ETFE, which in turn is bounded by an innermost layer made of PA.

[0004] The disadvantage of these known hydrogen pipes is that the permeability is still too high, so that too much hydrogen still diffuses through the pipes and is lost - particularly noticeable when the vehicles are idle for long periods.

[0005] This object is achieved by a pipe, in particular a use of a pipe, for conducting hydrogen, in particular in a vehicle, wherein the pipe encloses a lumen and comprises a plurality of layers, wherein the pipe has at least two barrier layers, wherein an inner barrier layer of the at least two barrier layers comprises a first plastic, wherein an outer barrier layer of the 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 a separating layer, wherein the pipe has a support layer, wherein the support layer is enclosed by the inner barrier layer, wherein the second plastic is a vinyl alcohol plastic.

[0006] The invention is based on the finding that the permeability of a barrier layer with respect to hydrogen is low when using a vinyl alcohol plastic. In principle, the permeability can be significantly reduced by increasing the thickness of the barrier layer. However, barrier layers made of vinyl alcohol plastic are quite brittle, which is critical for the numerous bends that such a pipe is usually subjected to. It has been found that if the barrier layer is too thick, this barrier layer develops microcracks significantly more frequently during the bending process. These microcracks lead to significantly greater permeability, so that increasing the thickness of the vinyl alcohol barrier layer represents only a very limited means of improving the barrier properties.

[0007] The invention is based, in particular, on the finding that providing a second barrier layer with a vinyl alcohol plastic and interposing a separating layer between the two barrier layers—while maintaining a consistently low cracking probability—allows for a significantly greater total layer thickness of barrier layers with a vinyl alcohol plastic. By providing two, three, or more vinyl alcohol barrier layers with a correspondingly large number of separating layers interposed, the total layer thickness of the combined layer thicknesses of the individual vinyl alcohol barrier layers can be multiplied compared to a single vinyl alcohol barrier layer, while the cracking probability and thus also the reject rate remain consistently low. The aforementioned problem is thus solved.

[0008] The term "layer" preferably means that one layer is distinguishable from another because these two layers have different material compositions. A layer does not necessarily have to consist of a single, integral or homogeneously distributed material composition. It is possible for a layer to have sublayers or plies that are themselves distinguishable from one another. Advantageously, a single ply consists of a single, homogeneously distributed material composition.

[0009] The term "vinyl alcohol plastic" preferably refers to polymers containing a vinyl alcohol monomer, and in particular, ethylene-vinyl alcohol copolymer (EVOH), polyvinyl alcohol (PVOH), and butenediol-vinyl alcohol copolymer (BVOH). It is possible for the vinyl alcohol plastic to be the sole plastic of the inner barrier layer and / or the outer barrier layer. According to one embodiment, the inner barrier layer and / or the outer barrier layer comprises a mixture of the vinyl alcohol plastic with a second or further materials, and in particular with a plastic or further plastics.

[0010] It is very particularly preferred that the pipe is a plastic pipe and preferably comprises at least 50, 70, 90, 95, or 97 wt.% plastic. Preferably, a / the protective layer and / or the support layer and / or the inner barrier layer and / or the separating layer and / or the outer barrier layer and / or the boundary layer comprises at least 50, 70, 90, or 95 wt.% of a plastic, in particular a thermoplastic. The pipe expediently has at least one, preferably at least two, three, four, or five bends. The pipe expediently has an outer diameter of at least 2 mm, 3 mm, or 4 mm.

[0011] It is particularly preferred that the separating layer comprises a plastic, preferably a polyamide and in particular PA 6. If the separating layer comprises a polyamide, the separating layer offers good toughness, whereby the more brittle barrier layers are separated from each other by a very robust, somewhat softer material. It is especially preferred that the separating layer comprises a softer material than the inner barrier layer and / or outer barrier layer. The term "softer" preferably refers to the Shore D hardness measured at room temperature and in particular to the standard DIN EN ISO 868:2003-10. The separating layer creates two thinner barrier layers, so that the layer composite of inner barrier layer, separating layer, and outer barrier layer has a lower overall brittleness. If the separating layer comprises PA 6, the separating layer is not only very robust but also adheres well to the inner barrier layer and the outer barrier layer.This ensures that the layer composite consisting of the inner barrier layer, separating layer, and outer barrier layer has little tendency to delaminate. The separating layer advantageously lies against the inner barrier layer and / or the outer barrier layer. The separating layer is expediently at least 0.05 mm, 0.06 mm, or 0.08 mm thick. The separating layer is preferably at most 0.3 mm, 0.4 mm, or 0.5 mm thick. Thicker separating layers tend to have the advantage that the barrier layers are separated further from one another, allowing even greater bends. Conversely, thinner layers are advantageous when the pipe needs to be as light or small as possible, which also saves material.

[0012] It is very preferred that the support layer comprises a material that is softer than that of the inner barrier layer. It is advantageous that the support layer rests against the inner barrier layer. The support layer advantageously comprises a plastic, preferably a polyamide and in particular PA 6. If the support layer comprises a softer material than the inner barrier layer or polyamide, the support layer stabilizes the inside of the inner barrier layer and thus particularly reduces the likelihood of cracks forming on the inside of the inner barrier layer. If the support layer comprises PA 6, this brings with it the advantages of the polyamide material and also the advantage of improved adhesion to the inside of the inner barrier layer, which reduces the likelihood of delamination when bent.It is possible for the support layer to be the innermost layer and preferably to contain an additive to increase conductivity. The additive can be conductive carbon black, for example. The layer thickness of the support layer may be at least 0.05 mm, 0.06 mm, or 0.07 mm. The layer thickness of the support layer is advantageously at most 0.5 mm, 0.4 mm, or 0.3 mm. It is very preferred for the layer thickness of the support layer to be smaller than the layer thickness of the separating layer. This is because, unlike the separating layer, the support layer does not have to separate barrier layers from one another, so that smaller layer thicknesses are generally sufficient here. The layer thickness of the support layer may preferably be at least 5%, 10%, 20%, 30%, or 50% smaller than the layer thickness of the separating layer.

[0013] According to a particularly preferred embodiment, the first plastic and / or the second plastic is an EVOH, a BVOH or a PVOH, wherein it is preferred that the first plastic and / or the second plastic is an EVOH or a PVOH. These three types of plastic are particularly preferred because they each have good barrier properties, are easy to process, and overall entail relatively low production costs. Since BVOH can be made significantly softer than EVOH and PVOH and at the same time is less advantageous than EVOH and PVOH with regard to production-specific hurdles, the present invention is particularly suitable for EVOH and PVOH. 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.Consequently, pipes with a low ethylene content in the EVOH particularly benefit from the present invention. Preferably, the ethylene content of the EVOH of the inner and / or outer barrier layer is at most 45%, 40%, 36%, or 33%, respectively. It is preferred that the inner and outer barrier layers have the same material composition. It is possible for the inner and outer barrier layers to have different material compositions.

[0014] According to a particularly preferred embodiment, the layer thickness of the inner barrier layer is less than or equal to (≤) the layer thickness of the outer barrier layer, and preferably smaller than the layer thickness of the outer barrier layer. This reduces the probability of cracking, while the combined thickness of the two barrier layers remains the same. This is because, under strong bending, the inner barrier layer is subjected to greater stress than the outer barrier layer, so that the outer barrier layer can be provided with a slightly greater layer thickness than the inner barrier layer. It is preferred that the layer thickness of the inner barrier layer is at least 5%, 10%, or 15% smaller than the layer thickness of the outer barrier layer. Preferably, the layer thickness of the inner barrier layer is at most 70%, 60%, or 50% smaller than the layer thickness of the outer barrier layer. The layer thickness of the inner barrier layer may preferably be at least 0.05 mm, 0.06 mm, or 0.08 mm.Advantageously, the layer thickness of the inner barrier layer is at most 0.5 mm, 0.4 mm, or 0.3 mm. Preferably, the layer thickness of the outer barrier layer is at least 0.06 mm, 0.07 mm, or 0.09 mm. Preferably, the layer thickness of the outer barrier layer is at most 0.6 mm, 0.5 mm, or 0.4 mm.

[0015] Preferably, the added thickness of the layer thicknesses of the inner barrier layer and the outer barrier layer is at least 0.11 mm, 0.12 mm, and 0.13 mm, respectively. It is preferred that the added thickness of the layer thicknesses of the inner barrier layer and the outer barrier layer amounts to at most 1.0 mm, 0.8 mm, 0.6 mm, and 0.4 mm, respectively. Expediently, the added thickness of the layer thicknesses of the inner barrier layer and the outer barrier layer amounts to at least 7%, 14%, and 20%, respectively, of the total wall thickness of the pipe. Preferably, the added thickness of the layer thicknesses of the inner barrier layer and the outer barrier layer amounts to at most 60%, 50%, and 40%, respectively, of the total wall thickness of the pipe. The total wall thickness of the pipe may be at least 0.5 mm, 0.8 mm, and 1.0 mm, respectively. Advantageously, the total wall thickness of the tube is a maximum of 4.0 mm, 3.5 mm or 3.0 mm.

[0016] It is possible for the pipe to have a third barrier layer and a second separating layer, the third barrier layer enclosing the outer barrier layer, the second separating layer being arranged between the outer barrier layer and the third barrier layer. It is preferred for the third barrier layer to comprise a plastic, the plastic preferably being a vinyl alcohol plastic. The vinyl alcohol plastic of the third barrier layer can be an EVOH, a PVOH, or a BVOH, with EVOH or PVOH being preferred. The plastic of the third barrier layer is particularly preferably an EVOH. The EVOH of the third barrier layer has an ethylene content of preferably at least 45%, 40%, 36%, or 33%. The third barrier layer expediently has the same material composition as the inner barrier layer and / or the outer barrier layer.The advantage of a third barrier layer is that the second separating layer further reduces the risk of cracking while maintaining the same thickness of the combined layer thicknesses of the three barrier layers.

[0017] It is preferred that the second separating layer comprises a plastic, in particular a polyamide and preferably PA 6. It is advantageous if the material of the second separating layer is softer than that of the outer barrier layer and / or the third barrier layer. This stabilizes the inside of the third barrier layer as well as the outside of the outer barrier layer. In the case of a polyamide, the separating layer has good mechanical properties, while in the case of PA 6 these good mechanical properties are further supported by good adhesion. The second separating layer expediently lies against the outer barrier layer and / or the third barrier layer.

[0018] Advantageously, the layer thickness of the second separating layer is smaller than the layer thickness of the boundary layer. It is preferred that the layer thickness of the second separating layer is greater than the layer thickness of the support layer. The layer thickness of the separating layer may be at least 0.05 mm, 0.06 mm, or 0.07 mm. Advantageously, the layer thickness of the second separating layer is at most 0.5 mm, 0.4 mm, or 0.3 mm.

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

[0020] According to a preferred embodiment, a boundary layer encloses the outer barrier layer or the third barrier layer, wherein the boundary layer preferably rests against the outer barrier layer or 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 support layer and / or thicker than the separating layer. A thick boundary layer is advantageous because it protects the pipe from the outside. This includes not only chemical but also, and above all, mechanical stresses, to which brittle and unprotected barrier layers can react sensitively. The layer thickness of the boundary layer may be at least 0.07 mm, 0.08 mm, or 0.09 mm. The layer thickness of the boundary layer is preferably at most 0.4 mm, 0.3 mm, or 0.2 mm.According to one embodiment, the boundary layer comprises only one layer, wherein the single layer 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 can comprise an additive with the aid of which the single layer of the boundary layer adheres better to the vinyl alcohol plastic. It is very preferred that the material of the single layer of the boundary layer is softer than the material of the outer barrier layer or a / the third barrier layer. This stabilizes an outer side of the outer barrier layer or the third barrier layer.

[0021] The pipe preferably comprises at least one adhesion promoter layer. According to one embodiment, the boundary layer comprises the adhesion promoter layer and a boundary layer, wherein the boundary layer preferably encloses the adhesion promoter layer. It is advantageous for the outer boundary layer to comprise a plastic, preferably a polyamide and / or a thermoplastic elastomer, in particular PA 6, PA 11, PA 12 and / or PA 612. The adhesion promoter layer is expediently arranged between the outer barrier layer or the third barrier layer and the boundary layer. Advantageously, the adhesion promoter layer rests against the outer barrier layer or the third barrier layer. Preferably, the adhesion promoter layer rests against the boundary layer. This arrangement makes it possible to provide other plastics that adhere less well to the vinyl alcohol plastic in order to reduce the possibility of delamination.Plastics with less good adhesion are, for example, PA 11, PA 12 or PA 612, which can be arranged on the outer barrier layer or the third barrier layer with the aid of an adhesion promoter, for example comprising a polyolefin and in particular polypropylene or polyethylene.

[0022] It is possible for the support layer to enclose a protective layer, with the protective layer preferably forming the innermost layer of the pipe. The protective layer preferably comprises a plastic and may in particular comprise a fluoropolymer or a polyamide. The fluoropolymer can be, for example, ETFE. The layer thickness of the protective layer may be at least 0.05 mm, 0.07 mm, or 0.09 mm. The layer thickness of the protective layer is expediently at most 0.3 mm, 0.25 mm, or 0.2 mm.

[0023] The innermost layer, especially the support layer or protective layer, advantageously contains an additive to increase conductivity. The additive can be conductive carbon black, for example.

[0024] The invention is explained below using three exemplary embodiments in three figures. Fig. 1 shows a cross section of a first pipe according to the invention, Fig. 2 shows a cross section of a second pipe according to the invention and Fig. 3 shows a cross section of a third pipe according to the invention.

[0025] The cross section of a first embodiment of a pipe 1 is shown in Fig. 1 shown. Accordingly, the tube 1 of this embodiment comprises a total of five layers (3, 4, 5, 6, 7) that enclose a lumen 2. From the inside out, the tube 1 of this embodiment comprises a support layer 3, an inner barrier layer 4, a separating layer 5, an outer barrier layer 6, and a boundary layer 7.

[0026] In the case of the inner barrier layer 4 and the outer barrier layer 6, these are layers which each comprise a vinyl alcohol plastic. In this exemplary embodiment, both barrier layers comprise an EVOH, whereby it is preferred that the inner barrier layer 4 and / or the outer barrier layer 6 consist of an EVOH. Preferably, the ethylene content of the vinyl alcohol plastic of the inner barrier layer 4 and / or the outer barrier layer 6 amounts to at most 35 mol% and more preferably to at most 33 mol%. According to a specific embodiment, the ethylene content of the inner barrier layer 4 and / or the outer barrier layer 6 amounts to 32 mol%. It is preferred that the inner barrier layer 4 and / or the outer barrier layer 6 consists of the vinyl alcohol plastic. Advantageously, the inner barrier layer 4 and the outer barrier layer 6 consist of the same material.In this embodiment, the layer thickness of the inner barrier layer 4 is 0.12 mm, while the layer thickness of the outer barrier layer 6 may be, for example, 0.15 mm.

[0027] It is very preferred that the separating layer 5 comprises a plastic, which is preferably a polyamide and particularly preferably PA 6. PA 6 adheres well to vinyl alcohol plastics and in particular to ethylene-vinyl alcohol copolymers, so that the separating layer 5, together with the two barrier layers 4, 6, forms a robust layered composite 4, 5, 6. In addition, polyamide or PA 6 is less brittle and tougher than the two barrier layers 4, 6 made of EVOH, so that the separating layer stabilizes the layered composite 4, 5, 6 in this respect as well. The basic idea of ​​the invention becomes clear from the layered composite 4, 5, 6, since the separating layer 5 allows the layered composite 4, 5, 6 to bend much better than a continuous barrier layer whose layer thickness is 0.27 mm and thus corresponds to the added layer thicknesses of the inner barrier layer 4 and the outer barrier layer 6.The layer thickness of the separating layer 5 may be 0.1 mm in this embodiment.

[0028] The support layer 3 preferably comprises a plastic and is preferably made of a plastic. The plastic of the support layer 3 can in particular comprise a polyamide, preferably PA 6. A typical layer thickness of the support layer may be 0.08 mm. In this exemplary embodiment, the support layer 3 is the layer which delimits the pipe 1 towards the inside and thus towards the lumen 2 and consequently also comes into contact with the hydrogen. In this respect, the support layer protects the inner barrier layer 4, for example, from leaching. In particular, however, the support layer 3 supports the relatively brittle inner barrier layer 4 on its inner side, so that the inner barrier layer 4 develops fewer cracks when bends are formed. In addition, the support layer 3 protects the inner barrier layer 4 when the pipe 1 is pushed onto a quick connector and experiences a press fit there.Advantageously, the support layer 3, when forming the innermost layer of the pipe 1, contains an additive that increases conductivity. This additive can be, for example, conductive carbon black, which makes the support layer 3, as the innermost layer, sufficiently conductive to avoid critical levels of electrical charging.

[0029] It is preferred that the tube 1 has a boundary layer 7 which is Fig. 1 forms the outermost layer of the pipe 1. In this exemplary embodiment, the boundary layer 7 is arranged directly on the outer barrier layer 6. The boundary layer 7 is advantageously made of a plastic or a polyamide or PA 6. The layer thickness of the boundary layer 7 may be 0.3 mm.

[0030] The Fig. 2The embodiment shown is a pipe 1 which is identical to the first embodiment with regard to the layers 3 to 6. In contrast to the first embodiment, however, the boundary layer 7 is formed in two layers. Thus, the boundary layer 7 of the second embodiment according to Fig. 2an adhesion promoter layer 8 and a boundary layer 9. The boundary layer 9 of this exemplary embodiment preferably consists of a plastic, in particular a polyamide and particularly preferably of PA 11 or PA 12. Due to the poorer adhesion of PA 11 or PA 12 to vinyl alcohol plastics, the adhesion promoter layer 8 is provided, which can, for example, comprise a polyolefin, in particular polypropylene or polyethylene. However, the adhesion promoter layer can also comprise an adhesion-modified polyamide or a polyamide 6. In this exemplary embodiment, the layer thickness of the adhesion promoter layer 8 may be 0.05 mm. The layer thickness of the boundary layer 9 can, for example, be 0.25 mm.

[0031] In Fig. 3 a third embodiment of a pipe 1 according to the invention is shown, which differs from the embodiment of Fig. 2It differs primarily in that the innermost layer of the pipe 1 is not formed by the support layer 3, but rather by a protective layer 10 adjacent to it. The protective layer 10 can, for example, comprise a polyamide or a fluoropolymer. The fluoropolymer is preferably an ETFE. The layer thickness of the protective layer 10 may be 0.15 mm. The protective layer 10 advantageously comprises an additive to increase the conductivity of the protective layer 10. The additive may, in particular, be conductive carbon black. List of reference symbols:

[0032] 1Pipe 2Lumen 3Support layer 4Inner barrier layer 5Separation layer 6Outer barrier layer 7Boundary layer 8Adhesion promoter layer of 7 9Boundary layer of 7 10Protective layer

Claims

1. Use of a pipe (1) for conducting hydrogen, in particular in a vehicle, the pipe (1) enclosing a lumen (2) and comprising a plurality of layers, the pipe (1) having at least two barrier layers (4, 6), an inner barrier layer (4) of the at least two barrier layers (4, 6) comprising a first plastics material, an outer barrier layer (6) of the at least two barrier layers (4, 6) comprising a second plastics material, the first plastics material being a vinyl alcohol plastics material, the barrier layers (4, 6) being separated from one another by a separating layer (5), the pipe (1) having a supporting layer (3), the supporting layer (3) being enclosed by the inner barrier layer (4), characterized in that the second plastics material is a vinyl alcohol plastics material.

2. Use according to claim 1, wherein the separating layer (5) comprises a plastics material, preferably a polyamide and in particular PA 6.

3. Use according to either of claims 1 or 2, wherein the supporting layer (3) comprises a material which is softer than that of the inner barrier layer (4).

4. Use according to any of claims 1 to 3, wherein the first plastics material and / or the second plastics material is an ethylene vinyl alcohol copolymer (EVOH), a butenediol vinyl alcohol copolymer (BVOH) or a polyvinyl alcohol (PVOH).

5. Use according to any of claims 1 to 4, 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).

6. Use according to any of claims 1 to 5, 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, 0.2 mm and 0.3 mm, respectively.

7. Use according to any of claims 1 to 6, wherein the pipe (1) has a third barrier layer and a second separating layer, wherein the third barrier layer encloses the outer barrier layer (6), wherein the second separating layer is arranged between the outer barrier layer (6) and the third barrier layer.

8. Use according to any of claims 1 to 7, wherein a boundary layer (7, 8, 9) encloses the outer barrier layer (6) or the third barrier layer and preferably comprises a plastics material, more preferably a polyamide and in particular PA 6, PA 11, PA 12 and / or PA 612.

9. Use according to any of claims 1 to 8, wherein the pipe (1) has at least one adhesion promoter layer (8), wherein preferably the boundary layer (7, 8, 9) comprises the adhesion promoter layer (8) and a boundary ply (9), wherein the boundary ply (9) preferably comprises a plastics material, in particular a polyamide, for example PA 11, PA 12 and / or PA 612.

10. Use according to any of claims 1 to 9, wherein the supporting layer (3) encloses a protective layer (10), wherein the protective layer (10) preferably forms the innermost layer of the pipe (1), wherein it is preferred that the protective layer (10) comprises a fluoropolymer, in particular ETFE.

11. Use according to any of claims 1 to 10, wherein the innermost layer (3, 10), in particular the supporting layer (3) or the protective layer (10), comprises an additive for increasing the conductivity, for example conductive carbon black.