Patent ID: 7579058

Claim:
An air-brake line, comprising: a first layer comprising a polyamide molding composition comprising at least 40% by weight of a polyamide having monomer units including an average of at least 8 carbon atoms; a second layer formed on the first layer, the second layer comprising an adhesion-promoting molding composition; a third layer formed on the second layer so that the second layer is interposed between the first layer and the third layer, the third layer comprising a polypropylene molding composition; a fourth layer formed on the third layer, the fourth layer comprising an adhesion-promoting molding composition; and a fifth layer formed on the fourth layer so that the fourth layer is interposed between the third layer and the fifth layer, the fifth layer comprising a polyamide molding composition comprising at least 40% by weight of a polyamide having monomer units including an average of at least 8 carbon atoms; wherein: an outer diameter of the pipe is in a range from 6 to 20 mm; a wall thickness of the pipe is in a range from 1.0 to 2.0 mm; a thickness of the second layer is in a range of from 0.02 to 0.2 mm; a thickness of the third layer is from 25 to 75% of the wall thickness; and the polypropylene molding composition comprises a polypropylene having a melt flow rate (MFR) measured by ISO 1133 (230° C./2.16 kg) in a range of from 0.1 to 3 g/10 mm.