RELATED APPLICATIONS

[0001] The present patent document claims the benefit of and priority to European Patent Application 18 158 183.6, filed February 22, 2018, and entitled“Multi-Layer Motor Vehicle Tube” the entire contents of which are incorporated herein by reference.

FIELD

[0002] The invention relates to a multi-layer motor vehicle tube, in particular, for conducting fuels, wherein the tube has at least five layers. The multi-layer motor vehicle tube according to the invention is employed, in particular, as a fuel pipe in vehicles. The motor vehicle tube may also be used as a vent line in tank ventilation systems. In this case, the tube is acted upon, in particular, by fuel vapors and their condensates.

BACKGROUND

[0003] Multi-layer motor vehicle tubes of the aforementioned kind are known from practice in different embodiments. Many of these known tubes have the disadvantage that the tube layers are exposed to undesirable erosions of layer components during the conduction of fuels. This affects above all the inner layer that is in contact with the fuel, but also the adjoining middle layers. The inner layers frequently contain oligomers in small amounts, which may be eroded by the fuel and are then deposited in the fuel system. There they may lead to problems, in particular, at nozzles and the like. The known tubes leave something to be desired with respect to their fuel resistance, or with respect to their resistance to the fuels. It is not for this reason alone that the barrier properties of these known tubes also fail to meet all requirements. The attempt was previously made to solve this problem by varying the layers -in particular, the inner layers. However, improvements in terms of undesired erosions were made at the expense of mechanical resistance and/or of the thermal resistance of the tubes. Many of these known tubes are also manufacturable only at great expense due to the choice of materials. This is true especially for motor vehicle tubes having inner layers made of fluoropolymers, in particular, of ETFE. ETFE has the further disadvantage that in the event of fire, it results in fluorine compounds that are hazardous and injurious to health.

SUMMARY

[0004] In contrast, the technical problem of the invention is to specify a multi-layer motor vehicle tube of the aforementioned kind, in which the disadvantages described above may be avoided, which exhibits both an improved chemical resistance and a resistance to erosions as well as a sufficient mechanical resistance and an optimal resistance to various temperatures, in particular, to higher temperatures. Moreover, this tube is intended to be optimally cost- efficient to manufacture.

[0005] To solve this technical problem, the invention teaches a multi-layer motor vehicle tube, in particular, for conducting fuels, wherein the tube has at least five layers, specifically having the following layer structure from the outside to the inside:

[0006] - an outer layer made of at least one polymer of the group "polyamide, polyolefin",

[0007] - carrier layer made of polyamide,

[0008] - a barrier layer made of at least one component of the group "ethylene-vinyl alcohol copolymer (EVOH), fluoropolymer",

- an intermediate layer,

[0009] - an inner layer made of polyethylene,

[0010] wherein the total layer thickness of the tube is 0.7 mm to 2.5 mm, particularly, 0.8 mm to 2 mm and preferably 0.85 mm to 1.8 mm. The total layer thickness of the tube is particularly preferably between 0.85 mm and 1.7 mm. [0011] According to one recommended embodiment of the invention, the outer layer of the tube is made of polyamide 12 or is made primarily of polyamide 12. Another recommended embodiment of the invention is characterized in that the outer layer is made of polyethylene or is made primarily of polyethylene. In this case, it is particularly preferred that the outer layer is made of HDPE or is made primarily of HDPE. - It is recommended that the thickness of the outer layer is 5% to 60%, particularly, 7% to 45% and preferably 10% to 40% of the total wall thickness of the tube. It is within the scope of the invention that the thickness of the outer layer is a maximum of 0.4 mm and falls preferably in the range of between 0.1 mm and 0.4 mm, very preferably in the range of between 0.2 and 0.4 mm.

[0012] A particularly recommended embodiment of the invention is characterized in that at least one adhesion promoting layer and preferably one adhesion promoting layer is interposed between the outer layer and the carrier layer. An adhesion promoting layer based on polyamide or based on a polyolefin is preferably employed. If an adhesion promoting layer based on polyamide is used, it is recommended to be a modified polyamide, particularly a modified polyamide based on polyamide 612. - If an adhesion promoting layer based on a polyolefin is employed, it is preferably a polyolefin modified with a carbonic acid derivative, preferably with a maleic acid derivative and very preferably with a maleic acid anhydride, in particular, polyethylene. - The thickness of the adhesion promoting layer is expediently 3% to 30%, particularly, 5% to 20% and preferably 5% to 15% of the total wall thickness of the tube. The thickness of the adhesion promoting layer is expediently 0.03 to 0.15 mm and particularly 0.03 to 0.1 mm.

[0013] A highly recommended embodiment of the invention is characterized in that the carrier layer is made of polyamide 6 or is made primarily of polyamide 6. In principle, the first carrier layer may also be made of at least one or may be made of one polyamide of the group“polyamide 612, polyamide 12, polyamide 10, polyamide 1 1 , co-polyamide 6/6.6, co-polyamide 6/12“. - It is within the scope of the invention that the thickness of the carrier layer is 5% to 70%, particularly, 10% to 60% and preferably 15% to 60% of the total wall thickness of the tube. The thickness of the carrier layer is expediently at least twice as thick and preferably at least three times as thick as the thickness of the adhesion promoting layer. It is recommended that the thickness of the carrier layer is 0.1 mm to 0.8 mm, particularly, 0.1 to 0.75 mm and preferably 0.2 to 0.6 mm. According to a proven embodiment of the invention, the carrier layer is thicker than the barrier layer and, particularly, at least twice as thick as the barrier layer. According to one embodiment variant of the invention, the carrier layer is at least 2.5 times as thick as the barrier layer. It is within the scope of the invention that the carrier layer is thicker than the outer layer and recommended to be at least 1.5 times thicker than the outer layer.

[0014] One embodiment of particular importance within the scope of the invention is characterized in that the barrier layer is made of ethylene vinyl alcohol copolymer (EVOH) or is made primarily of EVOH. This material, in combination with the additional layers according to the invention, has proven particularly successful as a barrier layer. - It is within the scope of the invention that the thickness of the barrier layer is 5% to 50%, particularly, 5% to 45% and preferably 10% to 40% of the total wall thickness of the tube. The thickness of the barrier layer is expediently 0.05 mm to 0.4 mm, particularly, 0.05 mm to 0.3 mm and preferably 0.75 to 0.25 mm.

[0015] One preferred embodiment of the invention is characterized in that the intermediate layer is made of polyamide 6 or is made primarily of polyamide 6. In principle, the second carrier layer may also be made of or may be made primarily of at least one polyamide or of one polyamide of the group“polyamide 612, polyamide 12, polyamide 10, polyamide 1 1 , co-polyamide 6/6.6, co-polyamide 6/12“. Within the scope of this preferred embodiment, the intermediate layer assumes the function of a second carrier layer. In terms of this embodiment, the carrier layer discussed above is also referred to below as the first carrier layer and the intermediate layer as the second carrier layer. It is within the scope of the invention that the thickness of the intermediate layer, respectively, the second carrier layer, is 5% to 70%, particularly, 10% to 60% and preferably 15% to 60% and very preferably 15% to 55% of the total wall thickness of the tube. The thickness of the intermediate layer, respectively, of the second carrier layer, is expediently 0.1 mm to 0.8 mm, particularly, 0.1 mm to 0.75 mm and preferably 0.2 mm to 0.6 mm. It is recommended that the intermediate layer, respectively, the second carrier layer, is thicker than the barrier layer and is preferably at least twice as thick as the barrier layer. According to one embodiment variant of the invention, the intermediate layer, respectively, the second carrier layer, is at least 2.5 times as thick as the barrier layer. It is also within the scope of the invention that the intermediate layer, respectively, the second carrier layer, is thicker than the outer layer, particularly, is at least 1.5 times thicker than the outer layer.

[0016] According to another preferred embodiment of the invention, the intermediate layer is formed as the adhesion promoting layer between the barrier layer and the inner layer. In this case, it is particularly an adhesive layer based on a polyamide and/or an adhesive promoting layer based on a polyolefin. In the embodiment variant with the adhesion promoting layer between the outer layer and the first carrier layer, this adhesion promoting layer is then a second adhesion promoting layer in the tube according to the invention. The same expediently applies to this second adhesion promoting layer as applies to the first adhesion promoting layer described above. The embodiments described there also apply to the second adhesion promoting layer between the barrier layer and the inner layer. This relates, in particular, to the material of the adhesion promoting layer and/or to the thickness of the adhesion promoting layer.

[0017] According to the invention, the inner layer is made of polyethylene or is made primarily of polyethylene. According to a very preferred embodiment of particular importance within the scope of the invention, the inner layer is made of HDPE or is made primarily of HDPE (high-density polyethylene). This material has proven particularly successful in terms of solving the technical problem. This inner layer acts as a kind of barrier layer against the components of the fuel or fuel vapor passing through and is distinguished by a very minimal erosion of layer components. - It is within the scope of the invention that the thickness of the inner layer is 5% to 55%, particularly, 7% to 50% and preferably 10% to 40% of the total wall thickness of the tube. The thickness of the inner layer is expediently 0.05 mm to 0.45 mm, particularly, 0.05 mm to 0.4 mm and preferably 0.1 mm to 0.35 mm. It is within the scope of the invention that the thickness of the inner layer is less than the thickness of the carrier layer. If, according to the embodiment discussed above, the intermediate layer is made of, or is made primarily of, polyamide, in particular, of polyamide 6, it is within the scope of the invention that the thickness of the inner layer is less than this second carrier layer made of polyamide. According to one embodiment variant of the invention, the inner layer is configured as an electrically conductive layer and is provided for this purpose with conductivity additives.

[0018] A particularly recommended embodiment of the invention is distinguished by the fact that the carrier layer has a greater thickness than the barrier layer. If the intermediate layer is made of, or is made primarily of, polyamide, in particular of polyamide (second carrier layer) according to the embodiment discussed above, it is further within the scope of the invention that this intermediate layer, respectively, second carrier layer, has a greater thickness than the barrier layer. The first carrier layer and/or the second carrier layer is/are expediently at least 1.2 times, particularly, 1.5 times and preferably 1.8 times thicker than the barrier layer. - According to a very preferred embodiment of the invention, the first carrier layer and/or the second carrier layer has/have a greater thickness than the inner layer. In this case, the first carrier layer and/or the second carrier layer is/are expediently at least 1.2 times and, particularly, at least 1.4 times and preferably at least 1.5 times thicker than the inner layer. - It is within the scope of the invention that the outer layer has a greater thickness than the barrier layer. The outer layer is particularly at least 1.1 times and preferably at least 1.2 time thicker than the barrier layer. - According to a recommended embodiment of the invention, the first carrier layer and/or the second carrier layer is/are thicker than the outer layer. The first carrier layer and/or the second carrier layer is/are particularly at least 1.2 times and preferably at least 1.3 times thicker than the outer layer.

[0019] It is within the scope of the invention that the outer layer guarantees an optimal protection against environmental influences. On the one hand, it is corrosion-resistant and chemically resistant to spray water, in particular, salt water as well as chemically resistant to oil and fuel. The two carrier layers guarantee, in particular, the mechanical stability of the tube according to the invention. The inner layer, like the barrier layer, has a barrier effect, specifically, in particular, against components of the fuel or fuel vapor flowing through the tube.

[0020] According to a preferred embodiment of the invention, the motor vehicle tube according to the invention is manufactured by extrusion or by co-extrusion of the layers. A very simple co-extrusion is possible with the layer components according to the invention and the co-extrusion may be carried out especially in moderate temperatures. - The tube according to the invention may also be formed as a smooth, unprofiled pipe or also as a corrugated pipe.

[0021] The invention is based on the finding that the motor vehicle tube according to the invention exhibits a superior chemical resistance and is resistant especially to erosions of layer components. This applies especially to the inner layer, but also to the adjoining layers. The tube according to the invention exhibits optimum barrier properties and a high resistance to fuel and aging. Particularly advantageous in this case is that one and the same tube according to the invention may be used for different fuels and offers the aforementioned advantages with respect to these various fuels. It is important to note that the tube according to the invention, in addition to the chemical resistance discussed, also exhibits an excellent mechanical resiliency. The tube according to the invention is further distinguished by an optimal thermal resistance and the tube may easily be used in a temperature range between -40°C and 140°C. The tube according to the invention may further be very cost-efficiently manufactured or may be manufactured from cost- efficient materials, as compared to many previously known tubes. It should further be emphasized that the materials of the layers of the tube according to the invention are very easy to process and a simple and problem-free co-extrusion of the layer sequence according to the invention is especially possible.

[0022] The invention is discussed in greater detail below with the aid of exemplary embodiments:

[0023] According to a first exemplary embodiment, the outer layer according to the invention is made of polyamide 12, or is made primarily of polyamide 12, and this outer layer has a recommended thickness of 0.15 mm to 0.4 mm. Attached directly to the outside layer, preferably on the inside, is an adhesion promoting layer, which is made preferably of a polyamide modified with maleic acid anhydride, in particular, polyamide 612. The adhesion promoting layer expediently has a thickness of 0.03 mm to 0.1 mm. Attached directly to the inside of this adhesion promotion layer is the first carrier layer, which is made of polyamide 6, or is made primarily of polyamide 6. It has a layer thickness of preferably 0.25 mm to 0.75 mm. Attached directly to the inside of the first carrier layer is the barrier layer, which is made of EVOH, or is made primarily of EVOH, and has a thickness of preferably 0.05 mm to 0.3 mm. Attached directly to the inside of the barrier layer is the intermediate layer in the form of a second carrier layer, which is made of polyamide 6, or is made primarily of polyamide 6, and has a recommended layer thickness of 0.25 mm to 0.75 mm. Attached to the inside of the second carrier layer is the inner layer, which is made of HDPE or is made primarily of HDPE and has a layer thickness of preferably 0.05 mm to 0.4 mm. The total wall thickness of this tube is preferably in the range between 0.7 mm and 2 mm.

[0024] According to a second embodiment of the invention, the outer layer is made of HDPE or is made primarily of HDPE and expediently has a layer thickness of 0.2 mm to 0.4 mm. Attached directly to the inside of the outer layer according to one preferred embodiment is an adhesion promoting layer, which is made of, or is made primarily, particularly, of a polyolefin modified with maleic acid anhydride - in particular, polyethylene - and has a layer thickness of preferably 0.03 mm to 0.1 mm. Attached directly to the inside of the adhesion promoting layer is the first carrier layer, which is made of polyamide 6, or is made primarily of polyamide 6, and has a recommended thickness of 0.2 mm to 0.75 mm. Attached directly to the inside of the first carrier layer is the barrier layer, which is made of EVOH or is made primarily of EVOH, and has a layer thickness of preferably 0.05 mm to 0.3 mm. Attached directly to the inside of the barrier layer is the intermediate layer, which is formed in this exemplary embodiment as an adhesion promotion layer and is made of, or is made primarily of, a polyolefin modified with maleic acid anhydride, in particular, polyethylene. This intermediate layer, respectively second adhesion promoting layer, has a thickness particularly of between 0.2 mm and 0.75 mm. Attached directly to the inside of the second carrier layer is the inner layer, which is made of HDPE, or is made primarily of HDPE, and has a layer thickness of preferably 0.1 mm to 0.4 mm. The total wall thickness of this tube is expediently between 0.8 mm and 2 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention is discussed in greater detail below with the aid of a drawing depicting merely one exemplary embodiment. In a schematic depiction:

[0026] Fig. 1 shows a perspective view of a tube according to the invention and

[0027] Fig. 2 shows a section through the object according to Fig. 1.

DETAILED DESCRIPTION

[0028] In the exemplary embodiment according to the figures, the tube 1 according to the invention has an outer layer 2, which is made of polyamide 12, or is made primarily of polyamide 12, and has a layer thickness of preferably between 0.2 mm and 0.4 mm. Attached to the inside of this outer layer 2 is an adhesion promoting layer 3, which is made, particularly and in the exemplary embodiment, of polyamide 612 modified with maleic acid anhydride. Attached to this inside of this is the first carrier layer 4, which is preferably and in the exemplary embodiment made of, or is made primarily of, polyamide 6 and expediently has a layer thickness of between 0.2 mm and 0.75 mm. Attached to the inside of this first carrier layer 4 is the barrier layer 5, which is preferably and in the exemplary embodiment made of EVOH, or is made primarily of EVOH, and has a recommended thickness of between 0.1 mm and 0.3 mm. Attached to the inside of this barrier layer 5 is the intermediate layer 6 in the form of a second carrier layer, which is made of polyamide 6, or is made primarily of polyamide 6, and has a layer thickness of preferably between 0.2 mm and 0.75 mm. Attached to the inside of the intermediate layer 6 is the inner layer 7, which is made of HDPE, or is made primarily of HDPE, and has a layer thickness of preferably between 0.1 mm and 0.4 mm. The multi-layer motor vehicle tube 1 depicted in the drawings has been manufactured by co-extrusion. It is within the scope of the invention that the inner layer 7 may be provided with conductivity additives.