Pipes and tubular conduits – Flexible – Distinct layers
Reexamination Certificate
2002-05-14
2002-10-22
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
Flexible
Distinct layers
C138S140000, C138S141000, C138SDIG007
Reexamination Certificate
active
06467509
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel hose having at least a rubber layer and a fluororesin layer formed on the inner surface thereof. The fuel hose of the invention is favorably used, for example, as a fuel hose for automobiles and exhibits excellent performance particularly for alcohol-containing gasoline and sour gasoline.
2. Description of the Related Art
In recent years, control led evaporation of fuel to the air has been demanded in relation to environmental pollution. Therefore, the fuel permeability of the fuel hose for automobiles has been more and more strictly regulated. Conventional fuel hoses prepared only from NBR/PVC have been unable to cope fully with such fuel permeation regulation. Further, the alcohol-containing gasoline used to purify automobile exhaust shows high permeation as compared with gasoline containing no alcohol. A fuel hose having further lower permeability to fuel has therefore been expected. Furthermore, when an automobile is left to stand for a long period of time, the gasoline may be compelled to remain in the gasoline tank for a long time to deteriorate the gasoline. Thus, the fuel hose should have low permeability and high resistance to such deteriorated gasoline (sour gasoline) as well.
The provision of a fluororesin layer excellent in low fuel permeability and resistance to sour gasoline is considered very effective to meet these requirements. However, since fluororesin has poor flexibility and sealing properties at hose joints, a fuel hose formed of a fluororesin layer alone is not suitable. It is thus reasonable to provide a thinned fluororesin layer, preferably as an inner layer of the fuel hose, and a rubber layer as an outer layer thereof. When the fluororesin layer is not provided at end portions of the fuel hose in order to ensure the sealing, it is preferable to impart to the rubber layer characteristics such as the resistance to sour gasoline since the rubber layer at the end portions may contact the gasoline.
The invention disclosed in Japanese Patent Application Laid-Open No. 118549/1996 exemplifies a conventional technique relating to the fuel hose of this kind. In this technique, a rubber layer prepared from epichlorohydrin unvulcanized rubber blended with an organic phosphonium salt and a fluororesin layer formed by extrusion are laminated and subjected to vulcanization.
The invention disclosed in Japanese Patent Application Laid-Open No. 169085/1996 also exemplifies the conventional technique. In this technique, a fluororesin layer is extruded and laminated between an outer rubber layer and an inner rubber layer and then subjected to vulcanization. Th e outer rubber layer is formed of epichlorohydrin unvulcanized rubber blended with a salt of 1,8-diazabicyclo[5,4,0]undecene-7 (DBU salt) and an organic phosphonium salt, and the inner rubber layer is formed of unvulcanized NBR or unvulcanized fluororubber blended with the DBU salt or the organic phosphonium salt.
The invention disclosed in Japanese Patent Application Laid-Open No. 255004/1994 also exemplifies the conventional technique. In this technique, first, the inner surface of a vulcanized rubber tube undergoes a pretreatment for adhesion such as sodium etching treatment, corona discharge treatment, or low-temperature plasma treatment. Subsequently, the inner surface treated undergoes electrostatic coating by use of fluororesin powder, and is heated and cooled to prepare a fuel hose having a fluororesin layer on the inner surface of the rubber tube.
Fluoropolymers in general have a disadvantage of having weak adhesion to rubber materials, and fluororesins in particular are serious in this defect. In preparation of the fuel hose having a rubber layer formed on the outer surface of a thinned fluororesin layer, the adhesion of both layers presents a serious problem.
The aforesaid Japanese Patent Application Laid-Open Nos. 118549/1996 and 169085/1996 relating to the conventional techniques disclose vulcanization adhesion of the fluororesin layer to an unvulcanized rubber layer. That is, they do not disclose a technique allowing adhesion of the fluororesin layer to a rubber layer vulcanized already. When the fluororesin layer and the unvulcanized rubber layer are allowed to adhere by vulcanization, electrostatic powder coating of the fluororesin layer onto the unvulcanized rubber layer is difficult. Therefore, the formation of a good thin fluororesin layer by the electrostatic powder coating is also difficult.
The conventional technique of the aforesaid Japanese Patent Application Laid-Open No. 255004/1994 relates to a technical problem in adhesion of the thinned fluororesin layer to the vulcanized rubber layer. However, means for solving this problem is to perform a pretreatment for adhesion such as sodium etching treatment, corona discharge treatment, and low-temperature plasma treatment to the inner surface of the rubber layer. These pretreatments for adhesion complicate the production process to deteriorate production efficiency and production cost.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a simple and effective means for allowing a thin fluororesin layer to adhere to a vulcanized rubber layer in a fuel hose.
A first aspect of the invention provides a fuel hose comprising a rubber layer and a fluororesin layer adhering to the inner surface thereof, wherein rubber forming the rubber layer contains from 2 to 15 phr (parts per 100 parts of rubber) of a phenol-type resin.
The fuel hose of the first aspect has excellent resistance to fuel and resistance to permeation because of the fluororesin layer formed and particularly shows high reliability for the alcohol-containing gasoline and sour gasoline. Particularly when the innermost layer of the fuel hose is the fluororesin layer, the fuel hose exhibits the resistance to fuel most efficiently.
Since the rubber forming the rubber layer of the fuel hose contains from 2 to 15 phr of the phenol-type resin, adhesion to the fluororesin layer can be ensured without relying upon the vulcanization adhesion. Accordingly, first, the fuel hose can avoid troubles such as blocking of the flow path and reduction in vibration durability of the fuel hose caused by weak adhesion of the rubber layer to the fluororesin layer. Secondly, the formation of the thin fluororesin layer can be satisfactorily performed through the electrostatic powder coating, because it requires no extrusion which is needed in vulcanization adhesion
Furthermore, resin in general tends to deteriorate in resin performance when adhesive agents are added thereto. In the first aspect, the phenol-type resin is added to the rubber forming the rubber layer, and no adhesion agent is added to the fluororesin forming the fluororesin layer, thus to avoid the deterioration in performance of the fluororesin layer.
When the content of the phenol-type resin in the rubber forming the rubber layer is less than 2 phr, adhesion to the fluororesin may be deteriorated, and the resistance of the rubber layer itself to the sour gasoline also tends to become insufficient, particularly when epichlorohydrin rubber is used. The content exceeding 15 phr may invite deterioration in mechanical properties, compression set, and low-temperature properties, although the resistance of the rubber layer itself to the sour gasoline is satisfactorily maintained.
In a second aspect of the invention, the fluororesin is melted and allowed to adhere to the inner surface of the rubber layer by the electrostatic powder coating, and thus the fluororesin layer according to the first aspect is formed.
In the second aspect, a good thin fluororesin layer is formed by the powder coating. Furthermore, the thin fluororesin layer can be formed with ease in an arbitrary form and at an arbitrary portion of the hose. The arbitrary form is, for example, a smooth tubular form, a corrugated form, or a tubular form having a concave portion for containing a seal ring or other concave and/or convex portions. The arbitrary portion of
Iio Shinji
Ito Hiroaki
Brinson Patrick
Jacobson & Holman PLLC
Tokai Rubber Industries Ltd.
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