the nano - scale fillers used according to the invention are chosen from the group comprising the metal or semi - metal oxides or oxide hydrates . in particular , the nano - scale fillers are chosen from the group comprised of oxides and oxide hydrates of an element chosen from the group comprising boron , aluminum , gallium , indium , silicon , germanium , tin , titanium , zirconium , zinc , yttrium and / or iron . in one particular embodiment of the invention the nano - scale fillers are either silicon dioxide or silicon dioxide hydrates . in one embodiment , the nano - scale fillers are present in the polyamide molding compound as a uniformly dispersed , layered material . prior to being incorporated into the matrix they have a layer thickness of 0 . 7 to 1 . 2 mm and an interlayer separation of the mineral layers of up to 5 nm . in the polyamide ( pa ) systems , in which the filler particle dimensions are in the nanometer range , there are the following effects : the thermal expansion coefficient is clearly reduced compared with the unfilled matrix polymers particularly in the processing direction , the finely distributed particles reduce the permeation of gases and liquids like water without reducing viscosity as in classically filled systems ( composites ). by virtue of the molecular reinforcement , mechanical properties are improved even at elevated temperatures . in order to specifically reduce water absorption by the hydraulic fuel , monolayer tubing made of so - called nano - composite materials or multilayer tubing can be used , whereby in the latter case at least one layer must comprise at least one layer of nano - composite material . such materials , that can be added at any stage in manufacturing the polymer , whereby they can be finely distributed in the nanometer range , are suitable as fillers for manufacturing nano composites . these are preferred minerals according to the invention that already have a layered structure such as layered silicates , double hydroxides such as hydrotalcite or even graphite . nano - fillers base on silicones , silica or silsesquioxanes ( see fig1 ) are also suitable . in the context of the invention , layered silicates are understood to be 1 : 1 and 2 : 1 layered silicates . in these systems , layers of sio 4 tetrahedrons are regularly linked together with layers comprised of m ( o , oh ) 6 - octahedrons , wherein m represents metal ions like al , mg , fe . in the 1 : 1 layered silicates one tetrahedron is connected with one octahedron layer respectively . examples of this are kaolin and serpentine minerals . in the case of the 2 : 1 layered silicates two tetrahedrons are combined with one octahedron layer respectively . if all octahedron sites are not available with cations of the required charge to compensate for the negative charge of the sio 4 tetrahedrons and the hydroxide ions , charged layers occur . this negative charge is balanced by the insertion of monovalent cations like potassium , sodium or lithium or divalent cations such as calcium into the space between the layers . examples of 2 : 1 layered silicates are talc , mica , vermiculites , illites and smectites , wherein the smectites to which belong montmorillonite , and which easily swell with water due to their layer charge . furthermore , the cations are easily accessible for exchange processes . the swellable layered silicates are characterized by their ion exchange capacity cec ( meq / g ) and their layer separation d l . typical values for cec are between 0 . 7 to 0 . 8 meq / g . the layer separation in a dry , untreated montmorillonite is 1 nm and increases up to 5 nm with swelling with water or coating with organic compounds . examples of cations that can be used for exchange reactions are ammonium salts of primary amines having at least 6 carbon atoms such as hexane amine , decane amine , dodecane amine , hydrated c 18 tall oil amines or even quaternary ammonium compounds such as ammonium salts of α -, ω - amino acids with at least 6 carbon atoms . other activation reagents containing nitrogen are the triazine - based compounds . such compounds are described , for example , in ep - a - 1 074 581 ; therefore , particular reference is made to that document . chlorides , sulfates or even phosphates are suitable anions . along with the ammonium salts , sulfonium or phosphonium salts such as tetraphenyl or tetrabutyl phosphonium halides , for example , can be used . since polymers and minerals commonly have very different surface tensions , coupling agents can be used according to the invention in addition for treating the minerals for cation exchange . when this is done , titanates or even silanes such as y - amino propyl triethoxy silane are appropriate . as polyamides ( pa ) for the molding compounds according to the invention , from which polymerizates of aliphatic c 6 - c 12 lactams or ω - amino carboxylic acids with 4 to 44 carbon atoms , preferably 4 to 18 carbon atoms , or polycondensates can be used advantageously for manufacturing the hydraulic lines according to the invention , which can be obtained by polycondensation of at least one diamine from the group comprising the aliphatic diamines with 4 to 12 c - atoms , the cyclo - aliphatic diamines with 7 to 22 c - atoms and the aromatic diamines with 6 to 22 c - atoms in combination with at least one dicarboxylic acid from the group comprising aliphatic dicarboxylic acids with 4 to 12 catoms , cycloaliphatic dicarboxylic acids with 8 to 24 c - atoms and aromatic dicarboxylic acids with 8 to 20 c - atoms . the ω - amino carboxylic acids or the lactams are chosen from the group comprising ε - aminocapronic acid , 11 - aminoundecanoic acid , 12 - aminododecanoic acid , ε - caprolactam , enanthlactam , ω - laurin lactam . furthermore , it is also possible according to the invention to use blends of the aforesaid polymerizates or polycondensates , respectively . appropriate diamines according to the invention , which are combined with a dicarboxylic acid , are 2 , 2 , 4 - or 2 , 4 , 4 - trimethyl hexamethylene diamine , 1 , 3 - or 1 , 4 - bis ( aminomethyl ) cyclohexane , bis ( p - amino cyclohexyl ) methane , m - or p - xylylene diamine , ethyl diamine , 1 , 4 diamino butane , 1 , 6 - diamino hexane , 1 , 10 - diamino decane , 1 , 12 - diamino dodecane , cyclohexyl dimethylene amine . examples of dicarboxylic acids are succinic acid , glutaric acid , adipic acid , pimelic acid , suberic acid , azelaic acid , and sebacic acid , dodecanedioic acid , 1 , 6 - cyclohexane dicarboxylic acid , terephthalic acid , isophthalic acid and naphthalene dicarboxylic acid . concrete examples of the ( co -) polyamides for the hydraulic line according to the invention are , therefore , such homo - or co - polyamides from the group comprising pa6 , pa66 , pall , pa46 , pa12 , pa1212 , pa1012 , pa610 , pa612 , pa69 , pa6t , pa6i , pa10t , pa12t , pa121 , mixtures thereof or co - polymers based on these polyamides , wherein pa11 , pa12 , pa1212 , pa10t , pa12t , pa12t / 12 , pa1ot / 12 , pa12t / 106 , palot / 106 are preferred . preferred , according to the invention , are also co - polymers based on the aforementioned polyamides such as , for example , pa12t / 12 , pa10t / 12 , pa12t / 106 and pa10t / 106 . furthermore , pa6 / 66 , pa6 / 612 , pa6 / 66 / 610 , pa6 / 66 / 12 , pa6 / 6t and pa6 / 6i can also be used according to the invention . the present invention relates also to a hydraulic line comprising at least one inner layer comprised of a molding compound based on polyamide molding compounds filled with nanoscale fillers , which have already been described above , a polyolefin interlayer or an interlayer comprised of a molding compound based on ethylene / vinyl alcohol co - polymers and a polyamide outer layer . as polyamides for the inner and outer layers those from the group comprising polyamide 6 , polyamide 11 , polyamide 46 , polyamide 12 , polyamide 1212 , polyamide 1012 , polyamide 610 , polyamide 612 , polyamide 69 , polyamide lot , polyamide 12t , polyamide 121 , mixtures thereof or co - polymers based on these polyamides , wherein polyamide 11 , polyamide 12 , polyamide 1212 , polyamide 10t , polyamide 12t , polyamide 12t / 12 , polyamide 10 / 12 , polyamide 12t / 106 , polyamide 10t / 106 are preferred , or from the group comprising polyamide 6 / 66 , polyamide 6 / 612 , polyamide 6 / 66 / 610 , polyamide 6 / 66 / 12 , polyamide 6 / 6t , polyamide 6 / 6i can be used . the polyolefin of the interlayer can be either polypropylene or a mixture of ethylene / α - olefin co - polymer and ethylene / alkyl ( meth ) acrylate / maleic anhydride or glycidyl ( meth ) acrylate co - polymer . preferably the polyamide for the inner layer will be chosen from the group comprising polyamide 12 , polyamide 6 , polyamide 610 , polyamide 612 . the polyolefin interlayer is comprised of polypropylene . according to this embodiment the outer layer can be comprised of polyamide 12 . in a further embodiment the inner layer can be comprised of a molding compound based on polyamide 6 , polyamide 46 , polyamide 66 , polyamide 69 , polyamide 610 or polyamide 612 followed by a layer of a molding compound based on ethylene vinyl alcohol copolymers , if required , with a bonding layer disposed therebetween and an outer layer comprised of polyamide 12 . such coupling agents are well - known to those skilled in the art . in this context , reference is made by way of example to this applicant &# 39 ; s de 101 10 964 . 4 . still other , conventional polymers , well - known to those skilled in the art , can be added in amounts up to 30 % by weight to these ( co -) polyamides for particular purposes . the ( co -) polymers used can include those common additives impact strength modifiers such as epm and epdm , elastomers or rubber reinforces or fillers , uv stabilizers , antioxidants , pigments , dyes , nucleating agents , crystallization accelerators , crystallization inhibitors , fluidizer , lubricants , defoaming agents , flame retardants , and agents improving electrical conductivity , all of which may be blended into the polymers . epm and epdm are added to the polyamide molding compounds preferably in quantities of 5 to 20 % by weight , in particular in quantities of 5 to 10 % by weight . a hydraulic line according to the present invention can be manufactured in one or a plurality of stages by injection molding , co - extrusion , extrusion - blow - molding , pressing or sheating process . the following examples explain the present invention more fully , but non - limitingly . materials used : polyamide 12 : highlyviscous pa12 with the following properties mvi , relative 275 ° c ., 5 ash fusion viscosity ( m - kg ( cm 3 / 10 content point (° c .) cresol ) min ) % standard pa12 178 2 . 25 20 0 . 1 pa12 nano - com - 178 2 . 18 13 4 posite na - montmorillonite treated with 30 meq / 110 g mineral methyl tall oil bis - 2 - hydroxyethyl ammonium chloride d l : 1 . 85 nm the nanocomposite molding compounds were manufactured on a 30 mm werner & amp ; pfleiderer zsk 25 double - screw extruder at temperatures between 240 and 280 ° c . accordingly , the polymer was added to the charger of the extruder and the mineral added in the charger zone of the extruder and / or to the melt . addition of the modified layered silicate was 6 % by weight . investigation of the molding compounds according to the invention and not according to the invention was done according to the following specifications : mvi : ( melt volume index ) at 275 ° c ./ 5 kg according to iso 1133 sz : impact strength according to iso 20 179 / l1u ksz : low - temperature impact strength according to iso 179 / lea yield stress : iso 527 stretch - to - break : iso 527 tensile mod . of elasticity : iso 527 pa12 nano - composite standard pa12 tensile modulus of dr . mpa 2500 1500 elasticity tensile modulus of cond . mpa 1900 1100 elasticity yield stress dr . mpa 55 45 yield stress cond . mpa 50 40 elongation to rupture dr . % 110 200 elongation to rupture cond . % 170 200 impact strength , cond . kj / m 2 n . e . n . e . 23 ° c . impact strength , cond . kj / m 2 n . e . n . e . − 30 ° c . notch impact strength , cond . kj / m 2 6 10 23 ° c . notch impact strength , cond . kj / m 2 7 7 − 30 ° c . hdt a ° c . 60 45 hdt b ° c . 130 115 for determining water absorption , monolayer tubing with dimensions of 8 × 2 . 25 mm was manufactured on a nokia tube extrusion machine . the tubing was then filled with anhydrous type dot3 or dot4 hydraulic fluid and sealed . then the tubing was placed in a water bath at 70 ° c . for 70 hours . thereafter , the water content of the hydraulic fluid was determined . the following table shows that in the tubing according to the invention , a clearly lower water absorption of the hydraulic oil occurs . water absorption water absorption dot3 dot4 standard pa12 2 . 7 3 . 2 pa12 nano - composite 1 . 4 1 . 8 although the invention has been described with reference to particular embodiments , it will be apparent to one of ordinary skill in the art that modifications of the described embodiments may be made without departing from the spirit and scope of the invention .