Plastic vehicle conduit fabricated by coextrusion.

p0001The invention relates to a motor vehicle pipeline made by co-extrusion, multi-layer of plastic. The term motor vehicle pipeline also includes hose lines in the invention. - A motor vehicle pipeline refers to the fact that the pipeline will be factory-installed in a motor vehicle. But it can also be installed in the way of maintenance or repair later. It is mainly the management of the fuel. The fuel may comprise an alcohol component. In that regard, it is a motor vehicle pipeline which esp. Is intended for the management of an alcoholic medium. The term alcoholic medium in this context means not only fuel with alcohol addition or composed mainly of alcohol fuel. The term alcoholic medium designates the extent z. B. the liquid windscreen washer system and the print medium of a braking system. As is known, is introduced into compressed air braking systems alcohol to prevent freezing of condensate. Alcohol means within the scope of the invention, esp. Of methyl alcohol and ethyl alcohol, and mixtures thereof with water, but also higher alcohols.

p0002The known motor vehicle pipeline, from which the invention proceeds (DE 38 21 723), consists of a tubular outer layer made ​​of polyamide 12. It determines the strength of the motor vehicle pipeline. Incidentally, a pipe inside closed protective layer of polyamide 6 or 6.6 or 11 or 12 is provided, which is connected via an intermediate layer to the outer layer of polyamide 12th The intermediate layer is be formed of a polyolefin. The known motor vehicle pipeline is also under specific operating conditions safely and with great life, ie Iangzeitig consumption, bar. Special conditions are present when the medium that carries the motor vehicle pipeline, z. B. surfactants having or releasing oxygen. This often leads to other than the automobile pipelines described above (DE 38 21 723) to environmental stress cracking and disturbing oxidations. On the other hand in the fuel containing plastics of known motor vehicle pipeline soluble substances, eg. As monomers or oligomers. It may happen then that the fuel from the multi-layered wall of the motor vehicle pipeline leaches soluble constituents. This affects the life of the known motor vehicle pipeline barely, but disturbs other reasons: If a motor vehicle after the initial filling with fuel a long time is, for example, shipped or weeks and months waiting for the delivery, changes in the fuel lines, the fuel composition. In the fuel contained alcohol and aromatics diffuse much faster through the multilayer pipe wall of the motor vehicle pipeline as the aliphatic components. By changing the fuel composition, the solubility of those substances which are previously extracted from the multi-layer tube wall change. Esp. the monomers and oligomers of polyamide 11 or of polyamide 12 enter this resting fuel to crystallize and thus precipitates. The presence of copper ions accelerates this crystallization behavior in addition in some cases. Copper ions in the fuel derived z. B. from collector wear a petrol pump. The precipitated substances can lead to filter blockages, possibly collect the movement of the float chamber of the carburettor Ver and hinder the float motion or clog the injectors for injection engines. Also, deposits can form on the control edges of the injection pump. Moreover, the tensile strength and toughness of the known motor vehicle pipeline are improved.

p0003The invention has for its object to provide a motor vehicle pipeline made by co-extrusion of plastics, not walk in the releasable substances of the plastics used in a disturbing extent in solution and furthermore characterized by a very high tensile strength and toughness.

p0004To achieve this object, the invention is produced by coextrusion motor vehicle pipeline made of plastic, consisting of a tubular outer layer made of polyamide 11 or 12, an intermediate layer of polyamide 6, a solution inhibitor layer of a copolymer of ethylene and vinyl alcohol and an inner layer of polyamide 6, wherein between the outer layer and the intermediate layer, a thin adhesive layer is interposed from polyethylene or polypropylene. For the usual stresses, the outer layer has a thickness of 0.2 to 0.7 mm. This also applies to the intermediate layer. According to a preferred embodiment of the invention, the solution inhibitor layer on an ethylene content of 30 to 45 mass%. Conveniently, the solution inhibitor layer has a thickness of 0.1 to 0.2 mm. The adhesive layer meets all the requirements and carries the composite also contribute to the tensile strength and toughness if it has active side chains of maleic anhydride and a thickness of 0.05 to 0.2 mm. The inner layer is carried out expediently extremely thin, for example, in a thickness of 0.1 to 0.3 mm or less.

p0005The advantages achieved can be seen in the fact that initially prevented by the solution inhibitor layer in the motor vehicle pipeline according to the invention that come out of this layer and the upstream to the outside layers of monomers, oligomers or other substances in solution. The inner layer can be as thin geh old are that the amount of leachable substances from it is vanishingly small and no longer interferes. There is also the possibility of the inner layer of a particularly treated polyamide 6 produce, does not contain detachable monomers and oligomers convenient. On the other hand is achieved by the described layer structure on composite effects a high tensile strength and toughness.

p0006In the following, the invention will by way of example, to the drawing a part of which shows a cross section through a pipeline according to the invention, explained in more detail.

p0007The figure shows a produced by coextrusion motor vehicle pipeline made of plastic. It consists of a tubular outer layer 1 made of polyamide 11 or 12. It has an intermediate layer 2 of polyamide 6 and a solution inhibitor layer 3 of a copolymer of ethylene and vinyl alcohol. An inner layer 4 made of polyamide 6 is connected. there is a thin adhesive layer 5 made of polyethylene or polypropylene between the outer layer 1 and the intermediate layer 2 made of polyamide. 6 The inner layer 4 Polyamide 6 is very thin. By coextrusion the layers described were placed in composite.

p0008The outer layer 1 and the intermediate layer 2 may have a thickness of 0.2 to 0.7 mm. The inner layer 4 is regularly set in contrast remarkably thin, in the wall thickness range of 0.1 to 0.3 mm. The solution inhibitor layer 3 consists of a copolymer of ethylene and vinyl alcohol, namely at a ethylene content from 30 to 540 mass%. Its thickness is in the range of 0.1 to 0.2 mm. The adhesive layer 5 may have active side chains of maleic anhydride and a thickness of 0.05 to 0.2 mm. As the material for the inner layer 4 6 can be used with a low monomer content according to the preferred embodiment of the invention, a post-condensed polyamide.