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
2002-04-15
2003-04-15
Teskin, Fred (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...
C525S329300, C525S338000, C525S343000, C525S387000, C526S080000, C526S087000
Reexamination Certificate
active
06548604
ABSTRACT:
TECHNICAL FIELD
This invention relates to a nitrile group-containing highly saturated copolymer rubber giving a crosslinked rubber product having excellent cold resistance, a crosslinkable rubber composition comprising the highly saturated copolymer rubber, and a crosslinked rubber product made by crosslinking the rubber composition.
BACKGROUND ART
In recent years, a nitrile group-containing highly saturated copolymer rubber represented by a hydrogenated acrylonitrile-butadiene copolymer rubber attracts attention. A nitrile group-containing highly saturated copolymer rubber has a reduced amount of carbon-carbon unsaturated bonds in the backbone chain as compared with an acrylonitrile-butadiene copolymer rubber, and thus, the highly saturated copolymer rubber has good heat resistance, oil resistance and ozone resistance.
However, the cold resistance of a highly saturated nitrile group-containing is occasionally reduced depending upon the content of a nitrite group and the content of carbon-carbon double bonds in the nitrile group-containing highly saturated copolymer rubber.
In general, cold resistance can be enhanced by reducing the content of an acrylonitrile group in an acrylonitrile-butadiene copolymer rubber. But, cold resistance of a nitrile group-containing highly saturated copolymer rubber is occasionally increased and occasionally not increased, when the content of a nitrile group is reduced.
To improve cold resistance of a nitrile group-containing highly saturated copolymer rubber, a nitrile group-containing highly saturated copolymer rubber comprising four kinds of monomer units. i.e. (a) &agr;,&bgr;-ethylenically unsaturated nitrile monomer units, (b) &agr;,&bgr;-ethylenically unsaturated carboxylic acid ester monomer units, (c) conjugated diene monomer units, and (d) saturated conjugated diene monomer units, was proposed in, for example, Japanese Unexamined Patent Publication No. S63-95242 and ibid. H3-109449. However, the proposed nitrile group-containing highly saturated copolymer rubber gives a crosslinked rubber product which is liable to occasionally exhibits insufficient cold resistance and physical properties varying when it is placed in contact with oil.
DISCLOSURE OF THE INVENTION
A primary object of the present invention is to provide a nitrile group-containing highly saturated copolymer rubber giving a crosslinked rubber product having good cold resistance, oil resistance and dynamic properties; a crosslinkable rubber composition comprising the highly saturated copolymer rubber; and a crosslinked rubber product made by crosslinking the rubber composition.
To achieve the above-mentioned object, the present inventors made extensive research and found that a nitrile group-containing highly saturated copolymer rubber having a specific monomer unit composition, and exhibiting a reduced temperature difference between the extrapolated glass transition-initiating temperature (Tig) and the extrapolated glass transition-ending temperature (Teg), as measured by the differential scanning calorimetry, which copolymer rubber is prepared by carrying out polymerization while the monomer concentration In a polymerization reaction mixture is controlled depending upon the reactivity of monomers, gives a crosslinked rubber product having good cold resistance, oil resistance and dynamic properties. Based on this finding, the present invention has been completed.
Thus, in one aspect of the present Invention, there is provided a nitrile group-containing highly saturated copolymer rubber comprising (a) 10 to 40% by weight of &agr;,&bgr;-ethylenically unsaturated nitrile monomer units, (b) 10 to 60% by weight of &agr;,&bgr;-ethylenically unsaturated carboxylic acid ester monomer units, (c) 0.01 to 21% by weight of conjugated diene monomer units, and (d) 14 to 69. 99 by weight of saturated conjugated diene monomer units, wherein the sum of monomer units (c) and monomer units (d) is in the range of 20 to 70% by weight, the ratio of monomer units (d) to the sum of monomer units (c) and monomer units (d) is at least 70% by weight, and the difference between the extrapolated glass transition-initiating temperature (Tig) and the extrapolated glass transition-ending temperature (Teg), as measured by the differential scanning calorimetry, is not higher than 10° C.
In another aspect of the present invention, there is provided a crosslinkable rubber composition comprising 100 parts by weight of the above-mentioned nitrile group-containing highly saturated copolymer rubber, and 0.1 to 5 parts by weight of a sulfur-containing vulcanizing agent or 1 to 16 parts by weight of an organic peroxide crosslinking agent.
In still another aspect of the present invention, there is provided a crosslinked rubber product made by crosslinking the above-mentioned crosslinkable rubber composition.
BEST MODE FOR CARRYING OUT THE INVENTION
(Nitrile Group-Containing Highly Saturated Copolymer Rubber)
The nitrile group-containing highly saturated copolymer rubber of the present invention rubber comprises (a) 10 to 40% by weight of &agr;,&bgr;-ethylenically unsaturated nitrile monomer units, (b) 10 to 60% by weight of &agr;,&bgr;-ethylenically unsaturated carboxylic acid ester monomer units, (c) 0.01 to 21% by weight of conjugated diene monomer units, and (d) 14 to 69.99% by weight of saturated conjugated diene monomer units, wherein the sum of monomer units (a) and monomer units (d) is in the range of 20 to 70% by weight, the ratio of monomer units (e) to the sum of monomer units (c) and monomer units (d) is at least 70% by weight, and the difference between the extrapolated glass transition-initiating temperature (Tig) and the extrapolated glass transition-ending temperature (Teg), as measured by the differential scanning calorimetry, is not higher than 10° C.
As specific examples of an &agr;,&bgr;-ethylenically unsaturated nitrile monomer forming the &agr;,&bgr;-ethylenically unsaturated nitrile monomer units (a), there can be mentioned acrylonitrile; &agr;-halogenoacrylonitrile such as &agr;-chloroacrylonitrile and &agr;-bromoacrylonitrile; and &agr;-alkylacrylonitrile such as mehacrylonitrile and ethacrylonitrile. Of these, acrylonitrile is preferable. The &agr;,&bgr;-ethylenically unsaturated nitrile monomers may be used either alone or as a combination of at least two thereof.
The content of &agr;,&bgr;-ethylenically unsaturated nitrile monomer units (a) in the nitrile group-containing highly saturated copolymer rubber is in the range of 10 to 40% by weight, preferably 12 to 35% by weight and more preferably 15 to 30% by weight. When the content of &agr;,&bgr;-ethylenically unsaturated nitrile monomer units (a) is too small, the resulting crosslinked rubber product has reduced oil resistance. In contrast, when the content of &agr;,&bgr;-ethylenioally unsaturated nitrile monomer units (a) is too large, the resulting crosslinked rubber product has poor rubber cold resistance.
As specific examples of an &agr;,&bgr;-ethylenically unsaturated carboxylic acid eater monomer forming the &agr;,&bgr;-ethylenically unsaturated carboxylic acid ester monomer units (b), there can be mentioned acrylates and methacrylates, which have an alkyl group having 1 to 18 carbon atoms, such as methyl acrylate, ethyl acrylate, butyl acrylate, n-dodecyl acrylate, methyl methacrylate and ethyl methacrylate; acrylates and methacrylates, which have an alkoxyalkyl group having 2 to 18 carbon atoms, such as methoxymethyl acrylate and methoxyethyl methacrylate; acrylates and methacrylates, which have a cyanoalkyl group having 2 to 18 carbon atoms, such as &agr;-cyanoethyl acrylate, &bgr;-cyanoethyl acrylate and cyanobutyl acrylate, acrylates and methacrylates, which have a hydroxyalkyl group having 1 to 18 carbon atoms, such as 2-hydroxyethyl acryalte, hydroxypropyl acrylate and 2-hydroxyethyl methacrylate; acrylates and methacrylates, which have an aminoalkyl group with alkyl groups each having 1 to 18 carbon atoms, such as dimethylaminomethyl acrylate, diethylaminoethyl acrylate and dimethylaminoethyl methacrylate; acrylates and metha
Kotsuji Hiroyuki
Tsukada Akira
Armstrong Westerman & Hattori, LLP
Teskin Fred
Zeon Corporation
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