Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2002-10-07
2003-12-02
Nolan, Sandra M. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S035700, C428S474400, C428S476300, C138S137000, C138S141000
Reexamination Certificate
active
06656553
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a laminated hose for fuel transportation (which is referred to simply as a hose for fuel in the present invention) excellent in the interlaminar adhesive strength and also excellent in the antistatic properties and fuel permeation-preventing properties.
More particularly, it relates to a hose for fuel which shows an interlaminar adhesive strength of at least 20 N/cm even at a high take-up speed of 50 m/min and which has a small dependency of the interlaminar adhesive strength on the take-up speed during the production of the hose.
BACKGROUND ART
Heretofore, a fluororesin is used in a wide range of fields, since it is excellent in heat resistance, chemical resistance, weather resistance, non-tackiness, low abrasion properties, low dielectric characteristics, etc. For example, as an important application of a laminate, a hose for fuel or the like may be mentioned which is used in an engine room of an automobile, where it is exposed to a severe condition such as a high temperature environment. The hose for fuel is a hose for pipings to transport a gasoline fuel containing an alcohol or an aromatic compound.
In recent years, the regulations relating to permeation of gasoline through a hose for fuel have become stricter, and as a counter measure to comply therewith, a hose for fuel having a multilayer structure such as a double layer structure, has been proposed. Especially for the inner layer which is directly in contact with the fuel, it is desired to use a resin having chemical resistance against a corrosive material such as ethanol or methanol present in the fuel and having a gas barrier property not to let such a material permeate therethrough. From this viewpoint, as a material for the inner layer, a fluororesin having heat resistance, chemical resistance and gas barrier properties, is considered to be one of the most preferred materials. However, in a case where static electricity is formed and charges are built up when a liquid fuel passes through the hose for fuel made of a fluororesin, it becomes necessary to discharge the formed static electricity by a method such as imparting conductivity to the fluororesin.
On the other hand, for the outer layer of the hose for fuel, it is common to employ a polyamide resin such as polyamide 6, polyamide 11 or polyamide 12 which is usually relatively durable.
A laminate constituting the hose for fuel, is required to have firm interlaminar adhesive strength to avoid interlaminar peeling during the processing or use. As a means to improve the adhesive strength, there may, for example, be mentioned a method of employing an adhesive resin, or a method wherein a fluororesin tube is preliminarily formed and subjected to surface treatment, and then, a polyamide resin is coated therearound. Especially, a coextrusion molding method employing an adhesive resin may be mentioned as a low cost method, since no surface treatment step is required.
Heretofore, when it was attempted to construct a hose for fuel having a laminated structure comprising an inner layer made of a fluororesin and an outer layer made of a polyamide resin, there was the following problem. Namely, as the fluororesin is essentially poor in the adhesive properties, no adequate adhesive strength can be obtained, even if a tube or film of a fluororesin is coated with a material made of a polyamide resin of the outer layer directly. Further, even when an adhesive strength of a certain degree can be obtained, the adhesive strength is likely to vary depending upon the type of the polyamide resin, and the adhesive strength tends to be practically inadequate in many cases.
Since it has been difficult to bond a fluororesin of the inner layer directly to the polyamide resin of the outer layer, it has been attempted to interpose an adhesive resin layer having an adhesive performance to both the fluororesin and the polyamide resin, between the two layers.
As such an adhesive layer to be interposed between the layers, for example, a mixture comprising a polyamide resin and a fluororesin (JP-A-7-53823, JP-A-7-53824, JP-A-8-156199, JP-A-4-224939, JP-A-8-258212, etc.), or an adhesive fluororesin (JP-A-9-194815, etc.) has, for example, been proposed.
However, even such a hose for fuel having an adhesive resin layer interposed, has had a problem that the adhesive strength between the fluororesin layer and the polyamide resin layer varies depending on the forming condition, particularly on the take-up speed, and an adequate adhesive strength can not constantly be obtained.
DISCLOSURE OF THE INVENTION
The object of the present invention is to solve the above-mentioned problems and to obtain a hose for fuel comprising an outer layer made of a polyamide resin and an inner layer made of a fluororesin, particularly an ethylene/tetrafluoroethylene copolymer, which is excellent in the adhesive strength between the inner layer and the outer layer and also excellent in the antistatic properties and fuel-permeation-preventing properties, whereby the interlaminar adhesive strength does not substantially depend on the take-up speed.
The present inventors have conducted an extensive study to solve the above-mentioned problems and as a result, have found that by laminating an adhesive polyamide resin and an adhesive ethylene/tetrafluoroethylene copolymer, a hose for fuel having a layered structure of at least two layers having such both layers bonded extremely firmly, can be obtained, and the present invention has been accomplished.
Namely, the present invention provides the following hose for fuel.
A hose for fuel having a laminated structure comprising an inner layer (A) made of an ethylene/tetrafluoroethylene copolymer and an outer layer (B) made of a polyamide resin, wherein the inner layer (A) is made of an ethylene/tetrafluoroethylene copolymer adhesive to a polyamide resin, and the outer layer (B) is made of polyamide 12(a) satisfying the formula (1), or a mixture of polyamide 12(a) satisfying the formula (1) and polyamide 12(b) satisfying the formula (2), wherein the polyamides 12(a) and 12(b) satisfy the formula (3) and are polyamide resins showing an adhesive strength of at least 20N/cm to the inner layer (A):
[COOH]+[NH
2
]≧2×10
2
/(17.8&eegr;
r(a)
−19.1) (1)
[COOH]+[NH
2
]<2×10
2
/(17.8&eegr;
r(b)
−19.1) (2)
&eegr;
r(b)
−&eegr;
r(a)
≧0.3 (3)
wherein [COOH] is the equivalent concentration of polyamide terminal carboxyl groups, [NH
2
] is the equivalent concentration of polyamide terminal amino groups, and &eegr;
r(a)
and &eegr;
r(b)
are the relative viscosities of polyamides 12(a) and 12(b), respectively.
BEST MODE FOR CARRYING OUT THE INVENTION
In the hose for fuel of the present invention, one constituting the inner layer (A) is basically an ethylene/tetrafluoroethylene copolymer (hereinafter sometimes referred to simply as ETFE).
Preferred as ETFE, is one having tetrafluoroethylene and ethylene copolymerized in a ratio of from 70/30 to 30/70 (molar ratio), or a copolymer having these monomers further copolymerized with at least one fluoroolefin or other copolymerizable monomer other than ethylene, such as propylene. More preferred is a copolymer having tetrafluoroethylene/ethylene/other copolymerizable monomer copolymerized in a molar ratio of 30 to 60/20 to 60/0 to 40, particularly 40 to 60/35 to 60/0 to 5.
As such other copolymerizable monomer, an &agr;-olefin such as propylene or butene, a fluoroolefin having hydrogen atoms in an unsaturated group, such as vinyl fluoride, vinylidene fluoride or a (perfluoroalkyl)ethylene such as (perfluorobutyl)ethylene, a vinyl ether such as an alkyl vinyl ether or a (fluoroalkyl)vinyl ether, a vinyl ester such as vinyl acetate or vinyl butyrate, a (meth)acrylate such as a (fluoroalkyl)acrylate or a (fluoroalkyl)methacrylate, or a monomer having no hydrogen atom in an unsaturated group except for tetrafluoroethylene, such as hexafluoropropylene or a perfluoro(alkyl viny
Isobe Noriyuki
Iwata Yoshiro
Nishioka Tomoharu
Asahi Glass Company Limited
Bruenjes Chris
Nolan Sandra M.
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