Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-12-26
2004-03-02
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S233000
Reexamination Certificate
active
06699936
ABSTRACT:
TECHNICAL FIELD
This invention relates to a rubber composition comprising a nitrile rubber and an epihalohydrin rubber. More particularly it relates to a rubber composition for hoses comprising a specific nitrile rubber, epihalohydrin rubber and a specific crosslinking agent, which has enhanced resistance to fuel oil permeation and cold resistance. This invention further relates to a hose having a layer comprised of a crosslinked product of the rubber composition for hoses.
BACKGROUND ART
For fuel hoses of automobiles, enhanced resistance to fuel oil permeation and cold resistance are required for controlling dissipation of fuel oil such as gasoline into the air and preventing embrittlement under severe cold conditions, for example, at a temperature of −30° C. As rubber materials for fuel hoses, nitrile rubber, a polyblend of nitrile rubber and vinyl chloride resin (PVC) and epihalohydrin rubber are widely used.
In recent years, regulations for controlling automobile exhaust have become tightened to preserve the environment. Thus, hoses having good resistance to fuel oil permeation are desired. As techniques for enhancing the resistance to fuel oil permeation, there can be mentioned an attempt of increasing the wall thickness of hoses and an attempt of using a rubber material having excellent resistance to fuel oil permeation. However, the increase of the wall thickness of hoses contradictory to requirement of weight-saving of automobiles. Recent tendency of miniaturization and high integration of automobile engines makes it difficult to install hoses with a thick wall within a limited space. Therefore a rubber material exhibiting excellent resistance to fuel oil permeation is eagerly desired.
To comply with the above-requirement, in the case of nitrile rubber hoses, an attempt of increasing the content of &agr;,&bgr;-ethylenically unsaturated nitrile monomer units in the nitrile rubber is considered. This attempt enhances the resistance to fuel oil permeation, but reduces the cold resistance. Thus the hoses cannot be used in cold districts.
In the case of hoses of the nitrile rubber/vinyl chloride resin, an attempt of increasing the content of &agr;,&bgr;-ethylenically unsaturated nitrile monomer units in the nitrile rubber and an attempt of increasing the proportion of PVC resin in the polyblend are considered. These attempts contribute to enhancement of the resistance to fuel oil permeation, but the cold resistance is reduced. Further PVC is not desired from the viewpoint of environment preservation.
In the case of hoses of epihalohydrin rubber, the resistance to fuel oil permeation increases with an increase of the content of epihalohydrin units in the rubber, but, the resistance to fuel oil permeation is sometimes not to the desired even though the rubber is an epihalohydrin homopolymer. That is, an improvement of resistance to fuel oil permeation to the satisfying extent has been difficult. Further, the increase of the epihalohydrin unit content in the rubber leads to reduction of the cold resistance.
DISCLOSURE OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide a hose having improved resistance to fuel permeation and cold resistance, and further to provide a rubber material used for the production thereof.
The present inventors made extensive researches to achieve the above-mentioned object, and have found that a rubber composition comprising a specific nitrile rubber (A), epihalohydrin rubber (B) and a specific crosslinking agent, wherein the ratio in amount of nitrile rubber (A)/epihalohydrin rubber (B) is in a specific range, exhibits enhanced resistance to fuel consumption and cold resistance. Based on this finding, the present invention has been completed.
Thus, in accordance with the present invention, there is provided a rubber composition for a hose, which comprises a nitrile rubber (A) comprising 45 to 55% by weight of &agr;,&bgr;-ethylenically unsaturated nitrile monomer units and 55 to 45% by weight of conjugated diene monomer units, an epihalohydrin rubber (B), and a crosslinking agent (C
A
) for the nitrile rubber (A) and/or a crosslinking agent (C
B
) for the epihalohydrin rubber (B); the amount of the nitrile rubber (A) being in the range of 25 to 80% by weight based on the sum of the nitrile rubber (A) and the epihalohydrin rubber (B); and further provided a hose having a layer comprised of a crosslinked product of the rubber composition.
BEST MODE FOR CARRYING OUT THE INVENTION
Rubber Composition
The rubber composition for a hose, of the present invention comprises a nitrile rubber (A) comprising 45 to 55% by weight of &agr;,&bgr;-ethylenically unsaturated nitrile monomer units and 55 to 45% by weight of conjugated diene monomer units, an epihalohydrin rubber (B), and a crosslinking agent (C
A
) for the nitrile rubber (A) and/or a crosslinking agent (C
B
) for the epihalohydrin rubber (B), wherein the amount of nitrile rubber (A) being in the range of 25 to 80% by weight based on the sum of nitrile rubber (A) and epihalohydrin rubber (B).
Nitrile Rubber (A)
The nitrile rubber (A) used in the present invention contains &agr;,&bgr;-ethylenically unsaturated nitrile monomer units and conjugated diene monomer units.
The &agr;,&bgr;-ethylenically unsaturated nitrile monomer is not particularly limited, and includes, for example, acrylonitrile and methacrylonitrile. Of these, acrylonitrile is preferable in view of the good resistance to fuel oil.
The content of &agr;,&bgr;-ethylenically unsaturated nitrile monomer units in nitrile rubber (A) is such that the lower limit is 45% by weight, preferably 47% by weight, and the upper limit is 55% by weight, preferably 53% by weight. If the content of &agr;,&bgr;-ethylenically unsaturated nitrile monomer units is too low, the resistance to fuel oil permeation is reduced. In contrast, if the content thereof is too high, the cold resistance is reduced.
The conjugated diene monomer is also not particularly limited, and includes, for example, 1,3-butadiene, 2-methyl-1,3-butadiene, 1,3-pentadiene and 2-chloro-1,3-butadiene. Of these, 1,3-butadiene is preferable in view of the good cold resistance.
The content of conjugated diene monomer units in nitrile rubber (A) is such that the lower limit is 45% by weight, preferably 47% by weight, and the upper limit is 55% by weight, preferably 53% by weight. If the content of conjugated diene monomer units is too low, the cold resistance is reduced. In contrast, if the content thereof is too high, the resistance to fuel oil permeation is reduced.
The nitrile rubber used in the present invention may contain other copolymerizable monomer units. The copolymerizable monomer includes, for example, &agr;-olefin monomers, &agr;,&bgr;-ethylenically unsaturated carboxylic acid monomers, &agr;,&bgr;-ethylenically unsaturated carboxylic acid ester monomers, &agr;,&bgr;-ethylenically unsaturated carboxylic acid amide monomers, vinyl aromatic monomers, carboxylic acid ester monomers of &agr;,&bgr;-ethylenically unsaturated alcohols, &agr;,&bgr;-ethylenically unsaturated ketone monomers and &agr;,&bgr;-ethylenically unsaturated ether monomers.
As specific examples of the &agr;-olefin monomer, there can be mentioned ethylene, propylene and 1-butene.
As specific examples of the &agr;,&bgr;-ethylenically unsaturated carboxylic acid monomer, there can be mentioned monocarboxylic acids such as acrylic acid and methacrylic acid; polycarboxylic acids such as maleic acid, fumaric acid and itaconic acid; and partial esters of polycarboxylic acids such an monobutyl fumarate ester, monobutyl maleate ester and monoethyl itaconate ester.
As specific examples of the &agr;,&bgr;-ethylenically unsaturated carboxylic acid ester monomer, there can be mentioned alkyl esters such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and lauryl methacrylate; alkoxy-substituted alkyl esters such as methoxyethyl acrylate and methoxyethoxyethyl acrylate; cyano-substituted alkyl esters such as cyanomethyl acrylate, 2-cyanoethyl acrylate, 2-ethyl-6-cyano
Fujita Shigeru
Nishimura Koichi
Ohkawa Toshio
Armstrong Kratz Quintos Hanson & Brooks, LLP
Tran Thao T.
Zeon Corporation
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