Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2001-05-25
2004-01-27
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S034100, C428S035700, C428S036600, C428S036800, C428S036900, C428S036910, C138S137000, C138S140000, C138S141000
Reexamination Certificate
active
06682796
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a fuel hose used for a fuel piping in a motor vehicle or the like. The fuel hose of this invention has a high resistance to gasoline, particularly alcohol-containing gasoline, sour gasoline and amine detergent. It is also suitably used for alcohol and hydrogen which are fuels for fuel cells.
2. Description of the Related Art
The necessity for reducing the amount of gasoline discharged into the atmosphere has recently been pointed out in connection with the environmental problems. Accordingly, the permeation of gasoline through the walls of fuel hoses in motor vehicles has come to be regulated still more strictly. Conventional fuel hoses having a single-layered wall of NBR/PVC (a mixture of acrylonitrile-butadiene rubber and polyvinyl chloride) or the like are not satisfactory for such regulations against the permeation of gasoline.
Alcohol-containing gasoline, which is used for cleaning the exhaust gas of a motor vehicle, is more likely to permeate through the wall of a fuel hose than gasoline not containing alcohol. This is another reason for a demand for a fuel hose having a wall which is less permeable to gasoline.
Therefore, it has been proposed that a fuel hose have a multilayered structure, and particularly that one layer in the multilayered structure be a fluororesin layer of very low permeability to gasoline. These proposals can be roughly classified into two groups depending on the processes employed. According to one group, an uncured rubber tube is laminated with an extruded fluororesin layer, and joined to it by curing. According to the other group, a fluororesin layer is formed on a cured rubber tube by a powder coating method.
One example of the former is disclosed in Japanese Patent Application Laid-Open No. 118549/1996. It discloses an invention in which an uncured tube of epichlorohydrin rubber containing an organic phosphonium salt is laminated with an extruded fluororesin layer and cured. Another example is disclosed in Japanese Patent Application Laid-Open No. 169085/1996. It discloses an invention in which an uncured outer rubber tube and an uncured inner rubber tube are laminated with a fluororesin layer extruded therebetween, and cured. The outer rubber tube is formed from uncured epichlorohydrin rubber containing a salt of 1, 8-diazabicyclo[5, 4, 0]undecene-7 (DBU salt) and an organic phosphonium salt. The inner rubber tube is formed from uncured NBR or fluororubber each containing a DBU salt or an organic phosphonium salt.
One example of the latter is disclosed in Japanese Patent Application Laid-Open No. 255004/1994. It discloses an invention of a fuel hose having a fluororesin layer formed on the inner surface of a cured rubber tube by electrostatically coating it with a fluororesin powder, followed by heating and cooling. According to this invention, pre-treatment, such as sodium etching, corona or low temperature plasma treatment, is applied to the inner surface of the rubber tube to ensure the adhesion between it and the fluororesin layer.
According to the former group of prior art as stated above, the rubber tube and the fluororesin layer adhere well to each other by adhesion in cure. The fluororesin layer formed by extrusion is, however, difficult to form with a small thickness of, say, 0.05 to 0.2 mm or less with good quality. Thus, it has been a problem that, as the fluororesin layer does not have a satisfactorily small thickness, the fuel hose loses flexibility, and eventually cracks, or has its wall layers separated from each other as a result of, for example, vehicle vibration. The fluororesin layer formed by extrusion has a substantially equal thickness along the whole length of the rubber tube. It has, therefore, been a problem that the fluororesin layer formed on the inner surface of the rubber tube makes the hose fail to form a tight seal at the hose connecting end. It has been another problem that a large force is required for the insertion of a pipe into a hose connecting end. It has been still another problem that the extruded fluororesin layer is difficult to form in a corrugated shape.
According to the latter group of prior art as stated above, however, it is easy to form the fluororesin layer with a thickness which is as small as, say, 0.05 to 0.2 mm, or even smaller. It is also possible to select that portion of the rubber tube which is to be coated with the fluororesin powder, and the thickness of its coating to be formed. It is, therefore, possible to form the fluororesin layer not reaching the hose connecting end and thereby avoid the problem of its sealing as pointed out above, when it is formed on the inner surface of the rubber tube. Even in the case where the fluororesin layer is so formed as to reach the hose connecting end, it is possible to form it with a smaller thickness adjacent to the hose connecting end and thereby reduce the force required for the insertion of a pipe thereinto. It is also easy to form the fluororesin layer in a corrugated shape.
In view of the foregoing, a fuel hose having a multilayered structure including a fluororesin layer is preferably manufactured by the latter process.
The latter process has, however, problems not pointed out in the above Japanese Patent Application Laid-Open No. 255004/1994, etc. A fluororesin usually employed for powder coating has a considerably high melting temperature. Therefore, the rubber tube is deteriorated by heat when the fluororesin applied by powder coating is melted and caused to adhere to the rubber tube. This problem may be avoided by using a fluororesin having a low melting temperature, such as a vinylidene fluoride homopolymer. A fluororesin having a low melting temperature is, however, so high in rigidity as to deprive the fuel hose of its flexibility, while not adhering to the rubber layer satisfactorily, either. Another problem is that the pre-treatment mentioned above, such as sodium etching, complicates the manufacturing process.
Under these circumstances, the inventors of this invention made an invention disclosed in Japanese Patent Application No. 196839/1998 (Laid-Open No. 82822/1999). It is a fuel hose having a wall comprising a rubber layer or layers and a fluororesin layer formed from a copolymer of vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE) and forming the innermost layer of the wall.
The fluororesin layer forming the innermost layer of the wall gives it high resistance and impermeability to alcohol-containing gasoline, sour gasoline, amine detergent, etc. As the fluororesin has a relatively low melting point, it is possible to avoid any deterioration of the rubber tube by heat when the molten fluororesin is caused to adhere to it. According to this prior application, at least the innermost layer of the rubber tube contains at least one of an organic ammonium salt, an organic phosphonium salt and a polyamine additive, so that a good adhesion can be obtained between the rubber tube and the fluororesin layer without relying upon vulcanization adhesion even if the fluororesin layer may be formed by powder coating.
It has, however, been found by further research that the use of a copolymer of VDF and CTFE as the fluororesin may somewhat reduce the gasoline impermeability of the hose. It has also been found that the addition of an organic ammonium or phosphonium salt, or a polyamine additive is effective for obtaining an improved initial adhesion between the rubber and fluororesin layers, but it is not always effective for maintaining an improved adhesion after the hose is filled with fuel.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a simple and effective method of obtaining both an improved initial adhesion between the rubber and fluororesin layers of a hose and an improved adhesion after the hose is filled with fuel, without allowing the deterioration of the rubber layer by heat or any lowering in gasoline impermeability of the hose.
According to a first aspect of this invention, there is provided a fuel hose comp
Iio Shinji
Ito Hiroaki
Aughenbaugh Walter B
Jacobson & Holman PLLC
Pyon Harold
Tokai Rubber Industries Ltd.
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