Pipes and tubular conduits – Flexible – Distinct layers
Patent
1995-10-13
1999-08-24
Hook, James F.
Pipes and tubular conduits
Flexible
Distinct layers
138141, 138DIG1, 138DIG3, F16L 1104
Patent
active
059412860
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
TECHNICAL FIELD
The present invention relates to the field of tubing manufacturing and in particular to the field of fuel and vapor transmission tubes for internal combustion engine vehicles. It further relates to laminated structures having flexibility, impact resistance and hydrocarbon impermeability suited for use as a fuel and/or vapor conducting tubing and to a process for making the same.
BACKGROUND OF THE INVENTION
It has been known in recent times to use a multilayered or laminated rubber structure serving as a fuel transporting hose for an automotive fuel feed line into a vehicle reservoir. The conduit wall may have three layers; a heat and gasoline-resistant inner tube; a weather-resistant outer tube and a reinforcing fiber matrix or layer interposed and integrated between the other two. Even so, partly oxidized, or "sour" gasoline and oxygenated fuel adversely affect a fuel hose life so that enhanced gasoline-resistant features are needed. The fluoropolymers FKM, a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidine chloride, hereinafter, respectively, TFE, HFE, and VF.sub.2, has exhibited satisfactory performance characteristics as a fuel resistant material. See, for example, U.S. Pat. No. 5,093,166, issued Mar. 3, 1992. However, it has proved difficult to bond an FKM layer to other rubbers. Further, FKM layers are not by themselves sufficiently impermeable to hydrocarbon vapors to enable automobile manufacturers to meet U.S. EPA standards for automotive vehicle emissions for 1995.
Thin layer THV, also a terpolymer of TFE, HFE, and VF.sub.2, has been used as a hydrocarbon barrier lamina in tubular hoses. These hoses have been made by spirally wrapping a THV tape on a mandrel to form a tube, spirally wrapping a metal reinforcement around the tube, and spirally wrapping a chloroprene tape around the reinforcement. The resulting tubular hose is heated to fuse the THV layers together and to vulcanize the rubber layer. This process is cumbersome and relatively expensive.
As to the automotive fuel filler tubes, some are presently made of relatively thick-walled nylon plastic, which provides the desired resistance to the usual hydrocarbon fuels, like gasoline, diesel oil, and even liquid paraffins, for example, ethanol. However, thick-walled nylon plastic tubing does not have sufficient flexibility and impact resistance to withstand automobile collisions without fuel line rupture. Flexibility and resilience of the tubing is also required to route the tubing through a tortuous path in the vehicle.
Vapor tubes which are used to recycle fuel vapors (for pollution control) must be resistant to the combustion vapors as well as the fuel itself. One of the more recent tubular construction is a coextruded formed tubing, which involves an inner core of NBR rubber and an outer core of a chlorosulphonated polyethylene plastic (Hypalon from the DuPont Co.). But with the currently used laminated fuel tubular conduits, there is still a persistent hydrocarbon pollution problem, due in part to the relatively high gas vapor permeability of presently used polymeric materials. In order to acceptably be used as fuel filler tubes, the conduits of these materials require at least surface modifications that will essentially block or markedly reduce unused HC vapor transmission to the environment from the fuel tank.
For example, the available Nitrile/Hypalon-based tubing has an HC permeation resistance rating of about 600 g/m.sup.2 per day vapor loss measurement using ASTM Reference Fuel C, while the federal EPA wants to reduce permeability emissions to about 2 g per day for the entire vehicle. To that end, the auto industry currently seeks to reduce permeability for the gasoline filler tube and other fuel lines, vapor lines and vent hoses essentially to zero, a goal that is addressed by the present invention.
SUMMARY OF THE INVENTION
According to the invention, a laminated rubbery structure includes the cooperative use of two fluoropolymeric materials having complement
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Browder William Troy
Dukes Glenn V.
Fauble Michael K.
Cadillac Rubber & Plastics, Inc.
Hook James F.
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