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
1999-11-02
2002-06-18
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S304000, C525S305000, C525S327300, C525S328900, C525S329600, C525S330500, C526S319000
Reexamination Certificate
active
06407179
ABSTRACT:
The present invention relates to an acrylic rubber excellent in oil resistance and excellent in the balance of heat resistance and cold resistance, and its composition.
In recent years, along with trends for large size and high speed of industry, rubber materials to be used for such industry are required to have higher durability. Especially, the trends for large size and high speed have brought about an increase of the operation temperatures of machines and apparatus, whereby the rubber materials are required to have higher heat resistance, and at the same time, rubber materials which are in contact with lubricating oils, are required to have the oil resistance improved.
Further, due to broadening of the industrial activities, the demand for cold resistance is required for rubber materials to be used in a severe environment of e.g. a cold area.
On the other hand, in an engine room of an automobile, the thermal conditions have been increasingly severer due to e.g. higher power of the engine or to cope with exhaust gas. Accordingly, for example, for lubricant resistant hoses for automobiles, acryl rubber excellent in the heat resistance and oil resistance has now been used instead of conventional nitrile-butadiene rubber. However, severity of the thermal conditions in the engine and engine room has created an environment wherein the engine oil itself undergoes deterioration, and it has been known that such deteriorated engine oil will attack a rubber hose to deteriorate the rubber material. Accordingly, the material for a lubricating oil hose to be used in an engine room is desired to have higher oil resistance, cold resistance and heat resistance than ever, and improvement of the performance is required also for acryl rubber which has now been used as a heat resistant/oil resistant material.
Further, due to a trend for high performance of lubricating oil for an automobile, the viscosity of the lubricating oil tends to be low, whereby further improvement in the oil resistance has been required.
JP-B-59-14498 discloses that a rubber composition comprising a vulcanizing agent and a copolymer of ethylene (A)/vinyl acetate (B)/an acrylate (C) wherein (C) is from 6 to 90 wt % and the weight ratio of (A)/(B) is at most 1, is excellent in the oil resistance, heat resistance and weather resistance.
Further, JP-A-63-312338 discloses a copolymer of ethylene with other copolymer components wherein the content of the ethylene component is from 3 to 10 wt %, wherein said other copolymer components comprise from 0 to 10 wt % of vinyl acetate, more than 20 and not more than 45 wt % of ethyl acrylate and at least 45 and less than 70 wt % of n-butyl acrylate, and its composition. JP-A-63-312339 discloses an acrylic rubber composition comprising an amine cross-linking agent and a copolymer comprising from 3 to 10 wt % of ethylene, from 0.1 to 10 wt % of a certain cross-linkable monomer and other copolymer components, wherein said other copolymer components comprise from 0 to 10 wt % of vinyl acetate, from 20 to 45 wt % of ethyl acrylate and from 45 to 70 wt % of n-butyl acrylate.
With these compositions, it is observed that the oil resistance may be improved to some extent, and with the latter, an improvement of the cold resistance is also observed to some extent. However, in view of the severity of the practical conditions as mentioned above, a further improvement has been desired in the balance of the oil resistance, cold resistance and heat resistance.
Accordingly, it is an object of the present invention to solve the above problems and to provide an acrylic rubber excellent in heat resistance and excellent further in the balance of the cold resistance and oil resistance, and its composition.
The present inventors have conducted an extensive study to solve the above problems and as a result, have found that a copolymer comprising monomer units of ethylene, monomer units of an alkyl acrylate and, if necessary, monomer units of a cross-linkable monomer in a certain specific compositional ratio, will present a rubber excellent in the balance of the cold resistance, oil resistance and heat resistance. The present invention has been accomplished on the basis of this discovery.
That is, the present invention provides an acrylic rubber comprising at least 0.1 and less than 3 wt % of monomer units of ethylene, from 0 to 10 wt % of monomer units of a cross-linkable monomer, and more than 87 and not more than 99.9 wt % of monomer units of at least one alkyl acrylate.
Now, the present invention will be described in detail with reference to the preferred embodiments.
The acrylic rubber of the present invention is an acrylic rubber comprising at least 0.1 and less than 3 wt % of monomer units of ethylene, from 0 to 10 wt % of monomer units of a cross-linkable monomer, and more than 87 and not more than 99.9 wt % of monomer units of at least one alkyl acrylate.
The monomer units of ethylene are particularly preferably from 0.5 to 2.5 wt %. If the monomer units of ethylene are too much, the oil resistance tends to be inadequate.
The alkyl acrylate to be used in the present invention preferably includes ethyl acrylate, n-butyl acrylate, methyl acrylate, n-propyl acrylate, isobutyl acrylate, n-pentyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-methylpentyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, n-decyl acrylate, n-dodecyl acrylate and n-octadecyl acrylate. Among them, an alkyl acrylate having a C
1-8
alkyl group is preferred, and ethyl acrylate and n-butyl acrylate are particularly preferred. The constituting ratio of alkyl acrylates is not particularly limited. However, from the viewpoint of the oil resistance, it is preferred that from 50 to 100 wt % of the alkyl acrylate is ethyl acrylate, or in the case where ethyl acrylate and n-butyl acrylate are used, the proportion of ethyl acrylate is form 50 to 100 wt %, based on the total amount of ethyl acrylate and n-butyl acrylate.
The acrylic rubber of the present invention may be one having other monomers copolymerizable with the above monomers co-polymerized within a range not to impair the object of the present invention. As such copolymerizable other monomers, alkyl acrylates such as cyanomethyl acrylate, 1-cyanoethyl acrylate, 2-cyanoethyl acrylate, 1-cyanopropyl acrylate, 2-cyanopropyl acrylate, 3-cyanopropyl acrylate, 4-cyanobutyl acrylate, 6-cyanohexyl acrylate, 2-ethyl-6-cyanohexyl acrylate and 8-cyanooctyl acrylate, may be mentioned. Further, alkoxyalkyl acrylates such as 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-(n-propoxy)ethyl acrylate, 2-(n-butoxy)ethyl acrylate, 3-methoxypropyl acrylate, 3-ethoxypropyl acrylate, 2-(n-propoxy)propyl acrylate and 2-(n-butoxy)propyl acrylate, may be mentioned.
Further, a fluorine-containing acrylate such as 1,1-dihydroperfluoroethyl (meth)acrylate, 1,1-dihydroperfluoropropyl (meth)acrylate, 1,1,5-trihydroperfluorohexyl (meth)acrylate, 1,1,2,2-tetrahydroperfluoropropyl (meth)acrylate, 1,1,7-trihydroperfluoroheptyl (meth)acrylate, 1,1-dihydroperfluorooctyl (meth)acrylate or 1,1-dihydroperfluorodecyl (meth)acrylate, a hydroxyl group-containing acrylate such as 1-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate or hydroxyethyl (meth)acrylate, a tertiary amino group-containing acrylate such as diethylaminoethyl (meth)acrylate or dibutylaminoethyl (meth)acrylate, a methacrylate such as methyl methacrylate or octyl methacrylate, an alkyl vinyl ketone such as methyl vinyl ketone, a vinyl or allyl ether such as vinyl ethyl ether or allyl methyl ether, a vinyl aromatic compound such as styrene, &agr;-methylstyrene, chlorostyrene or vinyltoluene, a vinyl nitrile such as acryl nitrile or methacrylonitrile, or an ethylenically unsaturated compound such as ethylene, propylene, vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, vinyl acetate, vinyl propionate or an alkyl fumarate, may be mentioned.
Among them, an alkoxyalkyl acrylate, such as 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-(n-propoxy)ethyl acrylate, 2-(n-butoxy)ethyl acrylate, 3-methoxypropyl acrylat
Abe Yasushi
Hagiwara Shogo
Koga Masao
Denki Kagaku Kogyo Kabushiki Kaisha
Oblon, Spivak, McClelland, Maier & Neustadt PC
Wu David W.
Zalukaeva Tanya
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