Polyamide- and EVOH-based multilayer tube for fluid transfer

Abstract

The present invention relates to a multilayer tube comprising, in its radial direction from the outside inwards: an outer layer formed from a polyamide, a layer formed from a copolyamide, a layer formed from an EVOH, a layer formed from a copolyamide, an inner layer formed from a polyamide, the layers being successive and adhering to one another in their respective contact region. Advantageously, the inner layer is formed by a compound based on a polyamide and electrically conducting carbon black, producing a surface resistivity of less than 10 6 Ω/?. The outside diameter of these tubes may range from 6 to 110 mm and the wall thickness may be from 0.5 to 5 mm. Advantageously, the petrol tube according to the invention has an outside diameter ranging from 6 to 12 mm and a total wall thickness of 0.36 mm to 1.95 mm, namely: a thickness of 50 to 700 μm for the polyamide outer layer, a thickness of 10 to 150 μm for the copolyamide layers, a thickness of 10 to 200 μm for the EVOH layer, a thickness of 100 to 500 μm for the polyamide inner layer possibly filled with electrically conducting carbon black. The tube of the present invention has a very low permeability to petrol, particularly to hydrocarbons and their additives, and in particular to alcohols, such as methanol and ethanol, or to ethers, such as MTBE or ETBE. These tubes also have good resistance to engine lubrication oils and fuels.

1 . A multilayer tube comprising, in its radial direction from the outside inwards: 
 an outer layer formed from a polyamide,    a layer formed from a copolyamide,    a layer formed from an EVOH,    a layer formed from a copolyamide,    an inner layer formed from a polyamide,    the layers being successive, and in which the copolyamide of the layers adjacent to the EVOH layer is a blend of a PA 6/12 copolyamide rich in 6 and of a PA 6/12 copolyamide rich in 12.    
     
     
         2 . Tube according to  claim 1 , in which the inner layer contains carbon black in an amount sufficient to produce a surface resistivity of less than 10 6  Ω/□.  
     
     
         3 . A tube according to  claim 1 , in which the polyamide of the outer layer is PA-11 or PA-12.  
     
     
         4 . A tube according to  claim 1 , in which the polyamide of the inner layer is PA-11 or PA-12.  
     
     
         5 . A tube according to  claim 1 , in which the copolyamides result from the condensation of at least two alpha, omega-aminocarboxylic acids or of at least two lactams having from 6 to 12 carbon atoms or of a lactam and an aminocarboxylic acid not having the same number of carbon atoms.  
     
     
         6 . A tube according to  claim 1 , in which the copolyamides result from the condensation of at least one alpha, omega-aminocarboxylic acid or a lactam, at least one diamine and at least one dicarboxylic acid.  
     
     
         7 . (Canceled)  
     
     
         8 . A tube according to  claim 1 , in which the copolyamide rich in PA-6 comprises 60 to 90% by weight of PA-6 for 40 to 10% of PA-12 respectively.  
     
     
         9 . A tube according to  claim 1 , in which the copolyamide rich in PA-12 comprises 60 to 90% by weight of PA-12 for 40 to 10% of PA-6 respectively.  
     
     
         10 . A tube according to  claim 1 , in which the proportions of the copolyamide rich in PA-6 and of the copolyamide rich in PA-12 are from 40/60 to 60/40 by weight.  
     
     
         11 . A tube according to  claim 3 , in which the polyamide of the inner layer is PA-11 or PA-12.  
     
     
         12 . A tube according to  claim 3 , in which the copolyamide of the layers adjacent to the EVOH layer is a blend of a PA 6/12 copolyamide rich in 6 and of a PA 6/12 copolyamide rich in 12.  
     
     
         13 . A tube according to  claim 4 , in which the copolyamide of the layers adjacent to the EVOH layer is a blend of a PA 6/12 copolyamide rich in 6 and of a PA 6/12 copolyamide rich in 12.  
     
     
         14 . A tube according to  claim 11 , in which the copolyamide of the layers adjacent to the EVOH layer is a blend of a PA 6/12 copolyamide rich in 6 and of a PA 6/12 copolyamide rich in 12.  
     
     
         15 . A tube according to  claim 1 , having the following thicknesses of the layers: 
 a thickness of 50 to 700 μm for the polyamide outer layer,    a thickness of 10 to 150 μm for the copolyamide layers,    a thickness of 10 to 200 μm for the EVOH layer,    a thickness of 100 to 500 μm for the polyamide inner layer.    
     
     
         16 . A tube according to  claim 15 , wherein the copolyamide layers have a smaller thickness than the inner and outer layers.  
     
     
         17 . A tube according to  claim 16 , in which the inner layer contains carbon black in an amount sufficient to produce a surface resistivity of less than 10 6  Ω/□.  
     
     
         18 . A tube according to  claim 3 , in which the copolyamide rich in PA-6 comprises 60 to 90% by weight of PA-6 for 40 to 10% of PA-12 respectively.  
     
     
         19 . A tube according to  claim 3 , in which the copolyamide rich in PA-12 comprises 60 to 90% by weight of PA-12 for 40 to 10% of PA-6 respectively.  
     
     
         20 . A tube according to  claim 3 , in which the proportions of the copolyamide rich in PA-6 and of the copolyamide rich in PA-12 are from 40/60 to 60/40 by weight.