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
2002-02-20
2003-12-02
Wilson, D. R. (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...
C525S328300, C525S381000, C525S382000, C525S194000
Reexamination Certificate
active
06657014
ABSTRACT:
TECHNICAL FIELD
This invention relates to a crosslinked rubber article having high heat resistance, high flex fatigue resistance, good elongation and low permanent set, and to a rubber composition capable of being crosslinked with steam and giving the crosslinked rubber article.
BACKGROUND ART
A nitrile group-containing highly saturated copolymer rubber is hitherto known as exhibiting good heat resistance, oil resistance and ozone resistance. A crosslinked article of the nitrile group-containing highly saturated copolymer rubber is used for various automobile parts such as a timing belt, a hose, a gasket, a packing and an oil seal. To develop a high-compact and high-powered engine, a rubber material having higher heat resistance is eagerly desired.
Among automobile parts, hoses are generally made by a process wherein an uncrosslinkable article prepared by extrusion of rubber material is subjected to steaming in a vulcanizer to be thereby crosslinked. When a highly saturated nitrile rubber having a sulfur crosslinking agent incorporated therein is used as a material for hoses, the resulting hoses have poor heat resistance and low mechanical strength. In contrast, when a highly saturated nitrile rubber having an organic peroxide crosslinking agent incorporated therein is used, a problem arises such that radicals of an organic peroxide is deactivated upon contact with air, and thus, there is a great difference in degree of crosslinking between the surface part of crosslinked hose and the inner part thereof. Consequently, a crosslinked rubber hose having high performance cannot be obtained with steam-crosslinking conducted after shaping.
When a highly saturated nitrile rubber is crosslinked with an organic peroxide crosslinking agent, a crosslinked rubber article having a reduced permanent set can be obtained. However, when the crosslinked rubber article has a hollow shape having cavity in the center such as o-ring, the reduction of permanent set is minor.
DISCLOSURE OF THE INVENTION
A primary object of the present invention is to provide a crosslinked article made of a nitrile group-containing highly saturated copolymer rubber having high heat resistance, high flex fatigue resistance, good elongation and low permanent set.
The present inventors carried out experimental research into crosslinking conditions of nitrile group-containing highly saturated copolymer rubber, and found that, when a nitrile group-containing highly saturated copolymer rubber having units of an ethylenically unsaturated dicarboxylic acid monoalkyl ester monomer is crosslinked with a polyamine crosslinking agent in the presence of a basic crosslinking accelerator, a crosslinked rubber article having desired good properties can be obtained. Based on this finding, the present invention has been completed.
Thus, in accordance with the present invention, there is provided a crosslinkable rubber composition comprising (a) 100 parts by weight of a nitrile group-containing highly saturated copolymer rubber containing units of an ethylenically unsaturated dicarboxylic acid monoalkyl ester monomer, (b) 0.5 to 10 parts by weight of a polyamine crosslinking agent, and (c) 0.5 to 10 parts by weight of a basic crosslinking accelerator.
In accordance with the present invention, there is further provided a crosslinkable rubber composition comprising (a) 100 parts by weight of a nitrile group-containing highly saturated copolymer rubber containing units of an ethylenically unsaturated dicarboxylic acid monoalkyl ester monomer, (d) 10 to 90 parts by weight of an acrylic rubber, (b) 0.5 to 10 parts by weight of a polyamine crosslinking agent, and (c) 0.5 to 10 parts by weight of a basic crosslinking agent, wherein said amounts of the polyamine crosslinking agent (b) and the basic crosslinking agent (c) are based on 100 parts by weight of the sum of the nitrile group-containing highly saturated copolymer rubber (a) and the acrylic rubber (d).
Further, the present invention provides a crosslinked rubber article made by crosslinking a crosslinkable rubber composition.
BEST MODE FOR CARRYING OUT THE INVENTION
Crosslinkable Rubber Composition (1)
The crosslinkable rubber composition (1) of the present invention comprises (a) 100 parts by weight of a nitrile group-containing highly saturated copolymer rubber containing units of an ethylenically unsaturated dicarboxylic acid monoalkyl ester monomer, (b) 0.5 to 10 parts by weight of a polyamine crosslinking agent, and (c) 0.5 to 10 parts by weight of a basic crosslinking accelerator.
[Nitrile Group-Containing Highly Saturated Copolymer Rubber]
The nitrile group-containing highly saturated copolymer rubber containing units of an ethylenically unsaturated dicarboxylic acid monoalkyl ester monomer (a) is (i) a rubber comprising ethylenically unsaturated dicarboxylic acid monoalkyl ester monomer units, &agr;,&bgr;-ethylenically unsaturated nitrile monomer units, &agr;-olefin monomer or diene monomer units, and optional units of other monomer copolymerizable therewith, or (ii) a rubber made of hydrogenating unsaturated bonds of the diene monomer units contained in the rubber (i).
The ethylenically unsaturated dicarboxylic acid monoalkyl ester monomer is an ester compound made from an ethylenically unsaturated dicarboxylic acid and an aliphatic alcohol. The ethylenically unsaturated dicarboxylic acid preferably has not larger than 5 carbon atoms, and, as specific examples thereof, there can be mentioned maleic acid, fumaric acid and itaconic acid. The aliphatic alcohol constituting the ester compound preferably has not larger than 5 carbon atoms. An aliphatic alcohol having a greater number of carbon atoms tends to give a copolymer rubber having a low rate of crosslinking and giving a crosslinked product having poor physical properties.
As specific examples of the ethylenically unsaturated dicarboxylic acid monoalkyl ester monomer, there can be mentioned maleic acid monoalkyl esters such as maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid mono-n-propyl ester, maleic acid monoisopropyl ester, maleic acid mono-n-butyl ester and maleic acid monoisobutyl ester; fumaric acid monoalkyl esters such as fumaric acid monomethyl ester, fumaric acid monoethyl ester, fumaric acid monopropyl ester and fumaric acid mono-n-butyl ester; and itaconic acid monoalkyl esters such as itaconic acid monomethyl ester, itaconic acid monoethyl ester, itaconic acid monopropyl ester and itaconic acid mono-n-butyl ester. Itaconic acid mono-n-butyl ester is especially preferable.
The content of ethylenically unsaturated dicarboxylic acid monoalkyl ester units in the nitrile group-containing highly saturated copolymer rubber (a) is preferably in the range of 0.5% to 15% by weight, more preferably 1% to 10% by weight and especially preferably 2% to 5% by weight. When this content is too small, the copolymer is liable to have reduced crosslinkability. In contrast, if this content is too large, a crosslinked rubber article tends to have poor water resistance because of residual carboxyl group in the crosslinked rubber article.
As preferable examples of the &agr;,&bgr;-ethylenically unsaturated nitrile monomer, there can be mentioned acrylonitrile, methacrylonitrile and &agr;-chloroacrylonitrile. Acrylonitrile is especially preferable. The content of &agr;,&bgr;-ethylenically unsaturated nitrile monomer units in the nitrile group-containing highly saturated copolymer rubber (a) is preferably in the range of 10% to 60% by weight, more preferably 15% to 55% by weight and especially preferably 20% to 50% by weight. When this content is too small, a crosslinked rubber article is liable to have poor oil resistance. In contrast, if this content is too large, a crosslinked rubber article is liable to have poor cold resistance.
The &agr;-olefin monomer preferably has 2 to 12 carbon atoms, and, as specific examples thereof, there can be mentioned ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene and 1-octene.
As specific examples of the diene monomer, there can be mentioned conjugated diene
Aimura Yoshiaki
Fujita Haruhiko
Kawanaka Takafumi
Kotsuji Hiroyuki
Mori Osamu
Armstrong Westerman & Hattori, LLP
Wilson D. R.
Zeon Corporation
LandOfFree
Crosslinkable rubber composition and crosslinked object does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Crosslinkable rubber composition and crosslinked object, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Crosslinkable rubber composition and crosslinked object will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3141433