Abstract:
A tubular structure having reduced fuel permeation for use in fuel filler and fuel vent hose application, wherein the tubular structure comprises a nitrile or a chlorinated polyethylene inner layer, a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer on the nitrile or chlorinated polyethylene inner layer, and a chlorinated polyethylene outer cover layer, and a method of forming such tubular structures are described. The tubular structure optionally includes a chlorinated polyethylene backing layer, one or more polyamide adhesive layers, and a reinforcement layer.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to the field of multilayer hoses, and particularly to the field of flexible polymeric hoses for use in fuel, chemical and vapor transport. 
         [0002]    Flexible polymeric hoses are generally used in a variety of uses such as automobile fuel feed hoses, fuel vent hoses, torque converter hoses, power steering hoses, air conditioner hoses, brake fluid hoses, industrial hydraulic hoses and compressed gas hoses, refrigerator hoses, garden hoses, propane gas hoses, etc. Various types of tubing construction have been employed to meet the needs of the various applications of hoses. For example, multilayer tubular structures are commonly used in the automotive industry as fuel and chemical transport hoses and fuel vent hoses. Choosing the right combination of materials used in the construction of such hoses is becoming more difficult due to environmental regulations, which severely limit the amount of fuel vapor that can permeate from the fuel system of a motor vehicle. Typically, fuel filler and vent hoses are multi layer tubular structures constructed of a natural or synthetic rubber material such as a conductive nitrile, e.g., acrylonitrile rubber, a fluoropolymer barrier layer such as a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer (THV) barrier layer, a nitrile backing layer, a reinforcement layer and 8 chlorinated polyethylene (CPE) cover layer. 
         [0003]    The overall cost and effectiveness of such hoses has proven to be somewhat disappointing. Therefore, there is a need for a fuel and chemical transport hose as well as a fuel vent hose which is more economical to produce and which exhibits improved properties. 
       SUMMARY OF THE INVENTION 
       [0004]    According to the present invention there is provided an improved multilayer tubular structure which is less costly to manufacture than prior multilayer fuel transport hoses and, in some cases, like fuel-alcohol blends, the fuel resistance of chlorinated polyethylene backing layer or cover layer is superior to the nitrile currently used as a backing layer. In addition to reduced permeability, the hose has adequate strength and durability over long periods of time, and is resistant to chemical degradation by the fluids being transported therein. 
         [0005]    Since it is well known in the industry that hoses used to transport fuels are required to contain a conductive agent or otherwise exhibit conductive characteristics in order to dissipate any electrical buildup which may occur during the flow of fuel through the hose, the hose of the hose of the present application contains therein such a conductive agent. 
         [0006]    In a first embodiment, the fuel and chemical transport hose of the present invention comprises: a conductive nitrile inner layer, a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer (THV) barrier layer, an adhesive layer, a chlorinated polyethylene (CPE) backing layer, a reinforcement layer, and a chlorinated polyethylene cover layer. 
         [0007]    In a second embodiment, the fuel and chemical transport hose of the present Invention comprises: a conductive nitrile inner layer, a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer, a reinforcement layer and a chlorinated polyethylene cover layer. 
         [0008]    In a third embodiment, the fuel and chemical transport layer of the present invention comprises: a conductive chlorinated polyethylene inner layer, an adhesive layer, a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer, an adhesive layer, a chlorinated, polyethylene backing layer, a reinforcement layer, and a chlorinated polyethylene cover layer. 
         [0009]    In a fourth embodiment, the fuel and chemical transport hose of the present invention comprises: a conductive chlorinated polyethylene inner layer, an adhesive layer, a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer, a reinforcement layer, and a chlorinated polyethylene cover layer. 
         [0010]    In a fifth embodiment, the fuel and chemical transport hose of the present invention comprises: a conductive nitrile inner layer, a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer, an adhesive layer, and a chlorinated polyethylene cover layer. 
         [0011]    In a sixth embodiment, the fuel and chemical transport hose of the present invention comprises: a conductive chlorinated polyethylene inner layer, an adhesive layer, a tetrafluoroethytene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer, an adhesive layer, and a chlorinated polyethylene cover layer. 
         [0012]    In those instances where the tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride (THV) is adjacent the chlorinated polyethylene layer, a polyamine adhesive is preferably used to adhere the CPE layer to the THV layer. 
         [0013]    Typically, the hoses of the present invention are useful as automobile fuel vent hoses, fuel filler hose, vapor lines and fuel feed lines. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view illustrating a first embodiment of the invention; 
           [0015]      FIG. 2  is a perspective view illustrating a second embodiment of the invention; 
           [0016]      FIG. 3  is a perspective view illustrating a third embodiment of the invention; 
           [0017]      FIG. 4  is a perspective view illustrating a fourth embodiment of the invention; 
           [0018]      FIG. 5  is a perspective view illustrating a fifth embodiment of the invention; and 
           [0019]      FIG. 6  is a perspective view illustrating a sixth embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    With respect to the drawings,  FIG. 1  is a tubular structure in accordance with a first embodiment of the invention where a tubular structure  10  is made from a nitrile polymeric material  11 , a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer  12  surrounding the outer surface of the nitrile layer  11 , an adhesive layer  13  on the surface of the tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer  12 , a chlorinated polyethylene layer  14  on top of the adhesive layer  13 , a reinforcement layer  15  surrounding the chlorinated polyethylene layer  18 , and a chlorinated polyethylene cover  16  surrounding the reinforcement layer and forming the outside layer of the tubular structure  10 . 
         [0021]      FIG. 2  is a tubular structure In accordance with a second embodiment of the invention where a tubular structure  20  is made from a nitrile polymeric material  21 , a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer  22  surrounding the outer surface of the nitrile layer  21 , a reinforcement layer  23  surrounding the tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer  22 , and a chlorinated polyethylene cover  24  surrounding the reinforcement layer and forming the outside layer of the tubular structure  20 . 
         [0022]      FIG. 3  is a tubular structure in accordance with a third embodiment of the invention where a tubular structure  30  is made from a chlorinated polyethylene material  31 , a first adhesive layer  32  on the outer surface of the chlorinated polyethylene material  31 , a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer  33  on top of the first adhesive layer  32 , a second adhesive layer  34  on the outer surface of the a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer  33 , a chlorinated polyethylene backing layer  35  surrounding the outer surface of the second adhesive layer  34 , a reinforcement layer  36  surrounding the chlorinated polyethylene backing layer  35 , and a chlorinated polyethylene cover  37  surrounding the reinforcement layer  38  and forming the outside layer of the tubular structure  30 . 
         [0023]      FIG. 4  is a tubular structure in accordance with a fourth embodiment of the invention where a tubular structure  40  is made from a chlorinated polyethylene material  41 , a first adhesive layer  42  surrounding the outer surface of the chlorinated polyethylene inner layer  41 , a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer  43  surrounding the first adhesive material layer  42 , a second adhesive layer  44  on top of the tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer  43 , a chlorinated polyethylene cover  45  surrounding the second adhesive layer  44  and forming the outside layer of the tubular structure  40 . 
         [0024]      FIG. 5  is a tubular structure in accordance with a fifth embodiment of the invention where a tubular structure  50  is made from a nitrile polymeric material  61 , a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer  52  surrounding the outer surface of the nitrile material  51 , an adhesive layer  53  surrounding the tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer  52 , and a chlorinated polyethylene cover  64  surrounding the adhesive layer  53  and forming the outside layer of the tubular structure  50 . 
         [0025]      FIG. 6  is a tubular structure in accordance with a sixth embodiment of the invention where a tubular structure  60  is made from a chlorinated polyethylene material  61 , a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer  62  surrounding the outer surface of the chlorinated polyethylene layer  61 , an adhesive layer  63  surrounding the tetrafluoroethytene-hexafluoropropylene-vinylidene fluoride terpolymer barrier layer  62 , and a chlorinated polyethylene cover  64  surrounding the adhesive layer  53  and forming the outside layer of the tubular structure  60 . 
         [0026]    Typically, the inner layer of the tubular structure is a nitrile material such as acrylonitrile-butadiene polymer. It has been found that, in certain application such as in the manufacture of a fuel filler hose or vapor hose, chlorinated polyethylene may provide an improved alternative to the nitrile as the inner layer of the tubular structure. 
         [0027]    The barrier layer of the tubular structure is a fluoropolymer which prevents or reduces the permeation of fuel, chemical and vapor through the barrier layer. Preferably, the barrier layer is a fluoropolymer containing polymerized units of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride. Preferably, the fluoropolymer is a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer having a fluorine content of about 67 to 73% by weight. 
         [0028]    The reinforcement materials useful in the present invention include natural and synthetic fibers such rayon, polyesters, aramid material, polyamides, e.g., nylon, polyimids, and any other suitable materials. 
         [0029]    Typically, the inner layer of the tubular structure contains a conductive material such as metal or carbon. Preferably, the conductive material is carbon in the form of carbon black, but may be any conductive agent or combination of conducting agents commonly recognized in the industry to provide conductivity to a rubber or plastic material. Examples of such conductive agents include elemental carbon in the form of carbon black and carbon fibrils, metals such as copper, silver, gold, nickel, and alloys or mixtures of such metals. The use of such conductive agents is known in the art to dissipate static electricity in the transportation of a fluid through the tubular structure. 
         [0030]    It is generally preferred to include an adhesive material between the chlorinated polyethylene layers and the tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer layers in order to prevent or reduce the likelihood of the two layers separating during use. 
         [0031]    Non-conducting polymer materials also may be employed as the inner layer in applications where dissipation of static electricity is not required. 
         [0032]    Other additives such as antioxidants, processing aids, etc. may be employed in amounts and methods known in the art. 
         [0033]    The tubular structures of the present invention are formed by extruding the various layers using simultaneous or tandem extrusion. 
         [0034]    Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent to those skilled in the art that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.