MULTI-LAYER FILLER PIPE FOR VEHICLE FUEL TANKS

Abstract: A filler pipe for use in a motor vehicle, contains an outer zone (1) and inner zone (2) which directly, abut each other, wherein the outer zone (1) contains a single layer of polyethylene and the inner zone (2) is capable of dissipating electrostatic energy and blocking the permeation of hydrocarbons.

Description: MULTI-LAYER FILLER PIPE FOR VEHICLE FUEL TANKS This patent application is related to U.S. Provisional Application Serial No. 60/084,568, which was filed May 7, 1998, the entire disclosure of which is incorporated herein by reference. FIELD OF THE INVENTION The present invention relates to a pipe for use in a motor vehicle, more specifically, to a multi-layer filler pipe for connection to a motor vehicle fuel tank. BACKGROUND OF THE INVENTION Filler pipes for connection to motor vehicle fuel tanks are subject to multiple design constraints, including those related to emissions tolerance, conductivity, price, weight, and durability. For example, the U.S. Clean Air Act Amendment of 1990 sets more stringent hydrocarbon emissions standards for all vehicles. So called light vehicles will be required to meet a diurnal standard of no more than 2 grams of emitted hydrocarbons per day. The diurnal standard will be phased in over the next few years, ending in the year 2000 with 100% compliance. Regarding conductivity, motor vehicle fuel possesses charged particles that can build up as the fuel moves across a non-conductive surface. When this charge is released in a localized area of a filler pipe, the discharge can degrade the strength of the pipe and lead to pipe failure, leaks, and fires. Thus, the surface over which fuel passes in a filler pipe should have sufficient surface conductivity to dissipate any electrostatic charge that may build up. Price constraints also define several design parameters. While fabrication costs are primary considerations, operation costs of the resulting vehicle are also closely monitored. These operation costs are functions of the vehicle's weight, which affects fuel consumption and efficiency. To address these concerns it is important to identify a low cost, lightweight material from which to construct a filler pipe. Fire is a constant threat in an automotive environment. A filler pipe should be resistant to this threat. Additionally, recent changes in European specifications have increased the fire resistance requirements for automobiles and their fuel systems in the European market. For these reasons it is important that the filler pipe be sufficiently resistant to fire. A filler pipe must also withstand the hazards of a motor vehicle environment, including corrosion and mechanical failure. Corrosive agents to which the pipe may be exposed include fuel, oil, brake fluid, and road salt. Mechanical phenomena that may act upon a filler pipe include deformation, fatigue, and vibration. For these reasons, it is important that the filler pipe material be sufficiently durable. In both Europe and the United States, new fuel systems are being considered to achieve these design criteria. In the United States, most vehicles utilize steel filler pipes. While steel pipes are relatively easy to manufacture, have good conductive properties, and are impermeable to hydrocarbons, they are undesirably heavy and subject to corrosion. In Europe, many vehicles are equipped with polymer-based filler pipes made of high density polyethylene. These pipes are low-cost and lightweight, but they have high permeation and most of them are non-conductive. Thus, European filler pipe technology possesses a significant disadvantage of failing to meet U.S. emissions requirements in a non-conductive embodiment. Fuel lines and vapor return lines of synthetic materials have been proposed. These lines possess some of the characteristics that are desirable in a modern filler pipe. However, the materials they are made out of, such as polyamides, are prohibitively expensive for use in filler pipe construction. These cost constraints are tolerated in fuel line construction due to additional design criteria that are not shared with filler pipes, such as high temperature and high pressure performance and reduced elongation characteristics. Various synthetic tubing materials have been suggested in the area of fuel line construction. WO 98/01694 to Hsich discloses a multi-layer tubing assembly for use in fuel line applications. An outer layer of a rubber-like multiphase polymer, e.g. polyamide, surrounds an intermediate adhesive layer and an inner layer of a semi- conductive fluoroplastic. The rubber-like multiphase polymer of the outer layer is selected from the group consisting of polymer blends or copolymers of polyamides, polyesters, polyurethane, and matallocene polyolefins. U.S. Patent No. 5,566,720 to Cheney proposes a two-layer fuel line composed of a thick corrosion-resistant outermost layer formed of a material, preferably a polyamide, that is durable and resistant to environmental degradation. An innermost fuel-contacting layer of a terpolymer is bonded to the thick outer layer. U.S. Patent No. 5,678,611 to Noone discloses a three-layer, co-extruded fuel line composed of an outer exterior wall of an extrudable polyamide, an inner hydrocarbon barrier layer, and an intermediate bonding layer. The inner hydrocarbon barrier layer may be capable of dissipating electrostatic energy, while the outer layer comprises a relatively thick layer of polyamide that is non-reactive with the external environment. It would be desirable to have a filler pipe that is highly impermeable to hydrocarbons and capable of discharging static electricity. Furthermore, the desired filler pipe would be resistant to fire and damage by fire. Finally, it would be desirable that this filler pipe be lightweight, inexpensive and resistant to chemical and mechanical degradation due to conditions in a motor vehicle environment. SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly impermeable, conductive, fire resistant, lightweight, inexpensive and sturdy filler pipe. Polyethylene, especially medium to high density polyethylene, is a durable material that is an inexpensive alternative to other durable synthetic materials, such as polyamides. A filler pipe made of polyethylene can be made with thicker walls due to polyethylene's lower cost and lighter weight. The added thickness and choice of material improve the filler pipe's resistance to fire while improving durability. A filler pipe constructed of an outer zone of polyethylene and a zone of a conductive barrier material is advantageously impermeable, conductive, fire resistant, lightweight, inexpensive, and resistant to chemical and mechanical degradation, thereby addressing the above-mentioned concerns and shortcomings of conventional filler pipe technology. In accordance with the present invention, the filler pipe comprises, in cross section, two zones that directly abut each other, wherein an outer zone comprises polyethylene and an inner zone comprises a material or materials capable of dissipating electrostatic energy and blocking the permeation of hydrocarbons. The above objects and advantages can be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. Additional objects and attendant advantages of the present invention will be set forth, in part, in the description that follows, or can be learned from practicing or using the present invention. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not to be viewed as being restrictive of the invention, as claimed. BRIEF DESCRIPTION OF THE DRAWING The accompanying drawings which are incorporated in, and constitute a part of, the specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention. Figure 1 is a sectional view through a wall of a piece of the pipe of an embodiment of the present invention; Figure 2 is a sectional view through a wall of a piece of the pipe of another embodiment of the present invention; Figure 3 is a sectional view through a wall of a piece of the pipe of another embodiment of the present invention; Figure 4 is a sectional view through a wall of a piece of the pipe of a further embodiment of the present invention; Figure 5 is a sectional view through a wall of a piece of the pipe of still another embodiment of the present invention; Figure 6 is a sectional view through a wall of a piece of the pipe of yet another embodiment of the present invention; Figure 7 is a sectional view through a wall of a piece of the pipe of the embodiment of Figure 6, with greater detail of the adhesive layer (14) of the inner zone (2). DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS All patents, patent applications and literatures cited in this description are incorporated herein by reference in their entirety. In the case of inconsistencies, the present disclosure, including definitions, will prevail. The present invention is a multi-layer filler pipe for connection to a motor vehicle fuel tank. The filler pipe is capable of transporting fluids, particularly those containing hydrocarbons. The filler pipe material is suitable for use in motor vehicles and comprises an outer zone that is resistant to the environment of a motor vehicle by being capable of withstanding impact from stones and road debris, various shocks, vibrational fatigue, and changes in temperature. Furthermore, the filler pipe material is able to withstand exposure to various corrosive or degradative agents to which it will be exposed through the normal course of operation of the motor vehicle, such as brake fluid, engine oil, road salt, gasoline, and the like. The filler pipe of the present invention comprises an outer zone and an inner zone. The filler pipe of the present invention can be fabricated by any suitable means, such as blow molding, co-extrusion, and the like. Co-extruding the given thermoplastic materials in a conventional co-extrusion process to form the outer and inner zones, however, is most preferred. The filler pipe can either be co-extruded to a suitable length or can be co-extruded in continuous length and subsequently cut to fit a given application. The various layers of the filler pipe construction are preferably bonded to one another and are preferably resistant to separation throughout the lifetime of the filler pipe. The filler pipe of the present invention can have any suitable wall thickness desired, as measured from the innermost wall of the inner zone to the outermost wall of the outer zone. The preferred wall thickness of the present invention, for use in automotive systems, will generally be between about 1.5 mm and about 3.0 mm, preferably about 2.0 mm to about 3.0 mm, most preferably, about 2.4 mm to about 2.6 mm. The outer zone (1 ) has a wall thickness sufficient to provide suitable strength and endurance to the multi-layer pipe of the present invention. "Outer zone" means that zone which is positioned radially outermost of the filler pipe. The outer zone (1 ) comprises a single layer of polyethylene that provides shape to the resulting filler pipe. The outer zone (1 ) polyethylene can also be made thick enough to provide adequate structure for mounting components to the filler pipe. It is resistant to fire, impact, vibrational shock, and the corrosive effects of a typical motor vehicle environment. The polyethylene used in the filler pipe of the present invention can be of any suitable grade, however, medium to high density polyethylene are preferred. The polyethylenes used in filler pipes can be medium or high density, depending on the process and desired end characteristics of the filler pipe. If the filler pipe is made using a blow molding process, then low melt index high density polyethylene is often preferred. Similarly, if the filler pipe layers are formed via co-extrusion, then either medium density polyethylene or high density polyethylene is often preferred. Environmental stress crack resistance is often considered an important design characteristic. If this is the case, then one should choose a grade of polyethylene with good environmental stress crack resistance properties. Other factors considered when choosing a polyethylene include the flex modulus and other mechanical properties. Examples of grades of polyethylene that may be used include, without limitation, the commercially available polyethylenes known as Solvay Fortiflex® G36-24-149, K44-24-123, and K44-08-123. The inner zone (2) is positioned radially innermost of the filler pipe. The inner zone (2) contains a material capable of serving as a hydrocarbon barrier layer to prevent significant permeation of the components of gasoline through to the outer zone (1 ) of the filler pipe and thus out to the surrounding environment. Suitable materials include, but are not limited to, chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride terpolymer, tetrafluoroethylene/ethylene copolymer, and polyvinylidene fluoride. The inner zone (2) has an innermost material with a surface oriented to come into direct contact with fuel traveling through the filler pipe. The selected material is suitably resistant to the corrosive effects of fuel. Examples of materials that can be used for the inner surface include, but are not limited to, high density polyethylene, chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride terpolymer, tetrafluoroethylene/ethylene copolymer, and polyvinylidene fluoride. Importantly, the selected innermost material in the inner zone (2) is capable of dissipating electrostatic energy. The material of the innermost layer of the inner zone (2) can include conductive material incorporated therein. The conductive material can be any suitable material of a composition and shape capable of electrostatic dissipation. Examples of conductive material that can be used include, without limitation, elemental carbon, stainless steel, silvered glass fibers, metalized textiles, and highly conductive metals such as iron, copper, silver, gold, nickel, silicon and mixtures thereof. The conductive metals can be present in the form of granules, flakes, fibers, and the like. The term "elemental carbon", as used herein, refers to materials commonly referred to as "carbon black". Preferably, the conductive material is co-extruded with the barrier materials employed in the inner zone (2) in sufficient quantity to permit electrostatic dissipation with resistivity less than, for example, about 10 6 ohm/sq. The amount of conductive material incorporated in the selected material of the innermost layer of the inner zone (2) is generally limited by considerations of low temperature durability and resistance to the degradative effects of the gasoline or fuel passing through the filler pipe. More specifically, the addition of conductive material can make the polymer susceptible to the permeation of hydrocarbons. If it is necessary to have a selected polymer with high conductivity such that the conductive polymer of the inner zone (2) is an insufficient barrier to hydrocarbons, then there shall be a second layer in the inner zone (2) which comprises a polymer selected from the group of chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride terpolymer, tetrafluoroethylene/ethylene copolymer, and polyvinylidene fluoride that does not contain added conductive material. If an adhesive layer is used, the adhesive should be chosen such that there is sufficient laminar adhesion between the adhesive and the two abutting layers that there will not be separation of the layers during the lifetime of the pipe. The adhesive should be compatible with polyethylene and the barrier layer. If a single adhesive is not compatible with both, then two different adhesive layers can be used: one compatible with polyethylene and the other compatible with the barrier layer, making sure that there is sufficient bonding between the two adhesives. It may also be desirable to use a mixture of two or more types of adhesives. It is known to use pressure sensitive adhesives, hot melt adhesives, and adhesive with cross-linkers when working with polyethylene. Such adhesives can be reactive or non-reactive, providing chemical or mechanical bonding. Examples of adhesives that possess such properties include, without limitation, Mitsui (America) Admer™ adhesive, Blemmer™ adhesive and mixtures thereof. Figure 1 depicts a preferred embodiment of the filler pipe of the present invention wherein the outer zone (1 ) is comprised of a single layer of polyethylene and the inner zone (2) is comprised of a single conductive layer (3) of the barrier material selected from the group consisting of conductive chlorotrifluoroethylene/ethylene copolymer, conductive polychlorotrifluoroethylene, and conductive tetrafluoroethylene/ethylene copolymer. There is sufficient laminar adhesion between the outer zone (1 ) layer and the inner zone (2) layer (3) to provide the desired level of laminar bonding. Figure 2 shows another preferred embodiment of the filler pipe of the present invention wherein the outer zone (1 ) is comprised of a single layer of polyethylene. The inner zone (2) is comprised of an outermost layer (4) of an adhesive and an innermost layer (5) of a conductive form of a barrier material selected from the group consisting of conductive chlorotrifluoroethylene/ethylene copolymer, conductive polychlorotrifluoroethylene, conductive tetrafluoroethylene/ hexafluoropropylene/vinylidene fluoride terpolymer, and conductive tetrafluoroethylene/ethylene copolymer. The adhesive layer (4) is capable of bonding to both the outer zone (1 ) layer and the innermost layer (5) of the inner zone (2) . Figure 3 shows a preferred embodiment of the filler pipe of the present invention wherein the outer zone (1 ) is comprised of a single layer of polyethylene. The inner zone (2) is comprised of an innermost layer (7) of a conductive form of a barrier material selected from the group consisting of conductive chlorotrifluoroethylene/ethylene copolymer, conductive polychlorotrifluoroethylene, and conductive tetrafluoroethylene/ethylene copolymer, and an outermost layer (6) of a non-conductive form of the same barrier material selected from the group consisting of chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene, and tetrafluoroethylene/ethylene copolymer. There is sufficient laminar adhesion between the outer zone (1 ) layer and the inner zone (2) outermost layer (6) to provide the desired level of laminar bonding. There is sufficient homogeneity between the conductive and the non-conductive forms of the selected barrier material to provide the desired level of laminar bonding between the innermost layer (7) and the outermost layer (6) of the inner zone. Figure 4 shows a preferred embodiment of the filler pipe of the present invention wherein the outer zone (1 ) is comprised of a single layer of polyethylene. The inner zone (2) is comprised of an innermost layer (9) of conductive polyethylene and an outermost layer (8) of a barrier material selected from the group consisting of chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene, and tetrafluoroethylene/ethylene copolymer. There is sufficient laminar adhesion between the outer zone (1 ) layer and the inner zone (2) outermost layer (8) and between the inner zone (2) innermost layer (9) and the inner zone (2) outermost layer (8) to provide the desired level of laminar bonding. Figure 5 shows a preferred embodiment of the filler pipe of the present invention wherein the outer zone (1 ) is comprised of a single layer of polyethylene. The inner zone (2) is comprised of an innermost layer (13) of polyethylene, an intermediate layer (11 ) of a barrier material selected from the group consisting of chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene, and tetrafluoroethylene/ethylene copolymer, and two adhesive layers (10 and 12). The outermost adhesive layer (10) is capable of bonding to both the outer zone (1 ) layer and the inner zone (2) outermost layer (8) to provide the desired level of laminar bonding. The innermost adhesive layer (12) is capable of bonding to both the inner zone (2) innermost layer (13) and the inner zone (2) intermediate layer (11 ) to provide the desired level of laminar bonding. Figure 6 shows a preferred embodiment of the filler pipe of the present invention wherein the outer zone (1 ) is comprised of a single layer of polyethylene. The inner zone (2) is comprised of an outermost layer (14) of an adhesive, an innermost layer (16) of the conductive form of a barrier material selected from the group consisting of conductive chlorotrifluoroethylene/ethylene copolymer, conductive polychlorotrifluoroethylene, conductive tetrafluoroethylene/ethylene copolymer, and conductive tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride terpolymer, and an intermediate layer (15) of the non-conductive form of the same barrier material selected from the group consisting of chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene/ethylene copolymer, and tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride terpolymer. The adhesive layer (14) is capable of bonding to both outer zone (1 ) layer and the inner zone (2) intermediate layer (15) to provide the desired level of laminar bonding. There is sufficient homogeneity between the conductive form of the barrier material and its non-conductive form to provide the desired level of laminar bonding between the innermost layer (16) and the intermediate layer (15) of the inner zone (2). In a preferred embodiment of Figure 6, the outer zone (1 ) is comprised of a single layer of polyethylene. The inner zone (2) is comprised of an innermost layer (16) of conductive polyvinylidene fluoride, an intermediate layer (15) of non- conductive polyvinylidene fluoride, and an outermost layer (14) of an adhesive. The adhesive is capable of bonding the outer zone (1 ) to the non-conductive layer (15) of polyvinylidene fluoride and can be selected, without limitation, from the group consisting of Mitsui (America) Admer™ adhesive, Blemmer™ adhesive and mixtures thereof. In a preferred embodiment shown in Figure 6, the adhesive layer (14) is a mixture of Admer™ and Blemmer™ adhesive. Alternatively, in a preferred embodiment shown in Figure 7, the adhesive layer (14) comprises an outermost sublayer of Admer™ adhesive (17) and an innermost sublayer of Blemmer™ adhesive (18). There is sufficient homogeneity between the conductive polyvinylidene fluoride and the non-conductive polyvinylidene fluoride to provide the desired level of laminar bonding between the innermost layer (16) and the intermediate layer (15) of the inner zone. The foregoing description of the preferred embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. Similarly, any process steps described might be interchangeable with other steps in order to achieve the same result. The embodiment was chosen and described to best explain the principles of the invention and its best mode practical application to thereby enable others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention specifically described herein.

Claims: WHAT IS CLAIMED IS: 1. A filler pipe for use in a motor vehicle, comprising an outer zone 1 and inner zone 2 which directly abut each other, wherein the outer zone 1 comprises a single layer of polyethylene and the inner zone 2 is capable of dissipating electrostatic energy and blocking the permeation of hydrocarbons. 2. The pipe of claim 1 wherein the inner zone 2 contains a radially innermost layer, comprising a conductive material selected from the group consisting of elemental carbon; stainless steel; silvered glass fibers; metalized textiles; highly conductive metals such as iron, copper, silver, gold, nickel, and silicon; and mixtures thereof; wherein the amount of the conductive material provides a surface resistivity in the innermost layer of less than about 10 6 ohm/sq. 3. The pipe of claim 2 wherein the selected conductive material is elemental carbon. 4. The pipe of claim 1 wherein the inner zone 2 comprises a layer 3, comprising a material selected from the group consisting of chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene and tetrafluoroethylene/ethylene copolymer. 5. The pipe of claim 1 wherein the inner zone 2 comprises an outermost radial layer 4 of an adhesive and an innermost radial layer 3, comprising a material selected from the group consisting of chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene/ethylene copolymer, and tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride terpolymer. 6. The pipe of claim 1 wherein the inner zone 2 comprises an outermost radial layer 6, comprising a material selected from the group consisting of chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene and tetrafluoroethylene/ethylene copolymer and an innermost radial layer 3, comprising a material selected from the group consisting of chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene and tetrafluoroethylene/ethylene copolymer. 7. The pipe of claim 1 wherein the inner zone 2 comprises an innermost radial layer 3, comprising polyethylene and an outermost radial layer 8, comprising a material selected from the group consisting of chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene, and tetrafluoroethylene/ethylene copolymer. 8. The pipe of claim 1 wherein the inner zone 2 comprises an outermost radial layer 10 of an adhesive, a first intermediate radial layer 11 of a material selected from the group consisting of chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene, and tetrafluoroethylene/ethylene copolymer, a second intermediate radial layer 12 of an adhesive, and an innermost radial layer 3, comprising polyethylene. 9. The pipe of claim 1 wherein the inner zone 2 comprises an outermost radial layer 14 of an adhesive, an intermediate radial layer 15, comprising a material selected from the group consisting of chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene/ethylene copolymer, and tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride terpolymer and an innermost radial layer 3, comprising a material selected from the group consisting of chlorotrifluoroethylene/ethylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene/ethylene copolymer, and tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride terpolymer. 10. The pipe of claim 1 wherein the inner zone 2 comprises an outermost radial layer 14 of an adhesive, an intermediate radial layer 15, comprising polyvinylidene fluoride, and an innermost radial layer 3, comprising polyvinylidene fluoride. 11. The pipe of claim 10 wherein the adhesive of the outermost radial layer 14 of the inner zone 2 comprises a combination of Blemmer™ adhesive and Admer™ adhesive. 12. The pipe of claim 10 wherein the adhesive of the outermost radial layer 14 of the inner zone 2 comprises an innermost radial sublayer 18 of Blemmer™ adhesive and an outermost sublayer 17 of Admer™ adhesive.

Inventors: MEHTA SAURIN, MEHTA, SAURIN
Applicants: MEHTA SAURIN, SOLVAY AUTOMOTIVE INC, MEHTA, SAURIN, SOLVAY AUTOMOTIVE, INC.
Application year: 1999
Main classification: F16L9
IPC codes: F16L9