Multilayer tube

Abstract

There is provided a multilayer resin tube having a plurality of thermoplastic resin layers, wherein an intermediate layer of the resin layers comprises an acid modified resin modified by the introduction of a functional group, and at least one layer is a barrier layer comprising an aromatic polyamide, for example, PA9T. The multilayer resin tube has good low-permeability attained with the use of an inexpensive resin, without using an expensive highly-functional resin such as a fluororesin.

1 . A multilayer resin tube having a multilayer structure of a plurality of thermoplastic resin layers, wherein an intermediate layer of the plurality of resin layers comprises an acid modified resin modified by the introduction of a functional group, and at least one adjacent layer is a barrier layer comprising an aromatic polyamide as a main component. 
   
   
       2 . A multilayer resin tube having a multilayer structure of three or more thermoplastic resin layers, said tube having a barrier layer comprising an aromatic polyamide as a main component, wherein an outer layer and an inner layer, lying outside and inside the barrier layer, each comprise an acid modified resin modified by the introduction of a functional group. 
   
   
       3 . The multilayer resin tube according to  claim 2 , wherein the barrier layer comprises PA9T. 
   
   
       4 . The multilayer resin tube according to  claim 3 , wherein the outer layer and the inner layer each comprise an ethylene/GMA (glycidyl methacrylate) copolymer. 
   
   
       5 . A multilayer resin tube having a multilayer structure of three or more thermoplastic resin layers, said tube comprising a barrier layer comprising an acid modified aromatic polyamide, modified by the introduction of a functional group, as a main component, and an outer resin layer and an inner resin layer, both adjacent to the barrier layer. 
   
   
       6 . The multilayer resin tube according to  claim 5 , wherein the barrier layer comprises acid modified PA9T. 
   
   
       7 . The multilayer resin tube according to  claim 3 , wherein the outer resin layer and the inner resin layer each comprise PA6, PA66, PA11 or PA12, or a mixture thereof. 
   
   
       8 . The multilayer resin tube according to  claim 6 , wherein the outer resin layer and the inner resin layer each comprise an acid modified PE resin. 
   
   
       9 . A multilayer resin tube having a multilayer structure of three or more thermoplastic resin layers, said tube having a layer comprising an acid modified resin modified by the introduction of a functional group, wherein an inner layer, lying inside the acid modified resin layer, is a barrier layer comprising an aromatic polyamide as a main component. 
   
   
       10 . The multilayer resin tube according to  claim 9 , wherein the acid modified resin layer comprises an acid modified aromatic PA9T and the barrier layer comprises PA9T. 
   
   
       11 . The multilayer resin tube according to  claim 9 , wherein the acid modified resin layer comprises an ethylene/GMA (glycidyl methacrylate) copolymer, and the barrier layer comprises PA9T or acid modified PA9T. 
   
   
       12 . The multilayer resin tube according to  claim 9 , wherein the acid modified resin layer comprises acid modified polyethylene, and the barrier layer comprises acid modified PA9T. 
   
   
       13 . The multilayer resin tube according to  claim 10 , wherein an outer layer, lying outside the acid modified resin layer, comprises PA6, PA66, PA11 or PA 12, or high-density polyethylene (HDPE), low-density polyethylene (LDPE) or linear low-density polyethylene. 
   
   
       14 . A multilayer resin tube having a multilayer structure of three or more thermoplastic resin layers, wherein a layer lying inside the outermost resin layer is a barrier layer comprising an acid modified aromatic polyamide, modified by the introduction of a functional group, as a main component. 
   
   
       15 . The multilayer resin tube according to  claim 10 , wherein the outermost resin layer comprises PA6, PA66, PA11 or PA12, or a mixture thereof. 
   
   
       16 . The multilayer resin tube according to  claim 14 , wherein the outermost resin layer comprises an ethylene/GMA (glycidyl methacrylate) copolymer. 
   
   
       17 . The multilayer resin tube according to  claim 10 , wherein the outermost resin layer comprises an acid modified PE resin. 
   
   
       18 . A multilayer resin tube having a multilayer structure of three or more thermoplastic resin layers, wherein the outermost resin layer comprises an acid modified resin modified by the introduction of a functional group, and a layer lying inside the acid modified resin layer is a barrier layer comprising an aromatic polyamide as a main component. 
   
   
       19 . The multilayer resin tube according to  claim 18 , wherein the outermost resin layer comprises an ethylene/GMA (glycidyl methacrylate) copolymer. 
   
   
       20 . A multilayer resin tube having a multilayer structure of five or more thermoplastic resin layers, wherein, in order from the outermost resin layer, the first layer is a PE (polyethylene) resin layer, the second and fourth layers are each an acid modified PE (polyethylene) resin layer, the resin being modified by the introduction of a functional group, and the third or fifth layer is a barrier layer comprising an aromatic polyamide. 
   
   
       21 . The multilayer resin tube according to  claim 1 , wherein the innermost layer comprises a crosslinked polyethylene resin. 
   
   
       22 . The multilayer resin tube according to  claim 1 , wherein the proportion of the acid modified resin(s) (excluding ethylene/GMA copolymer) in all the resins of the tube is less than 50% by weight. 
   
   
       23 . The multilayer resin tube according to  claim 8 , wherein the acid modified PE resin has a tensile breaking strength of not less than 12 MPa, a breaking elongation of not less than 300% and an MFR of not less than 0.5 g/min. 
   
   
       24 . The multilayer resin tube according to  claim 1 , wherein the resin (excluding PA) of the first layer has a density of 0.90 to 1.5 g/cm3, a flexural modulus of not less than 850 MPa and an environmental stress crack resistance of not less than 200 hr. 
   
   
       25 . The multilayer resin tube according to  claim 1 , wherein the innermost layer is a conductive resin layer.