Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-03-08
2003-01-14
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S098000, C524S302000, C524S324000, C524S495000
Reexamination Certificate
active
06506827
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a rubber composition and a vulcanized rubber composition. In more particular, the invention provides a rubber composition which comprises as the main component an ethylene-&agr;-olefin copolymer rubber and/or ethylene-&agr;-olefin-non-conjugated diene copolymer rubber, but is free from any zinc-containing compounds that would cause trouble at the time of use of the final products, as well as a vulcanized rubber composition with improved age resistance obtained by vulcanizing the rubber composition.
BACKGROUND OF THE INVENTION
There have been widely used for radiator hoses, heater hoses and radiator packings ethylene-&agr;-olefin copolymer rubbers and ethylene-&agr;-olefin-non-conjugated diene copolymer rubbers typically represented by ethylene-propylene rubber (EPM) and ethylene-propylene-non-conjugated diene rubber (EPDM). Usually in such uses, the ethylene-&agr;-olefin copolymer rubber and ethylene-&agr;-olefin-non-conjugated diene copolymer rubber are vulcanized with an organic peroxide and used as a vulcanized rubber. In this instance, it has been a common practice in the rubber technology to incorporate, for the purpose of preventing ageing, a zinc-containing compound typically represented by zinc white (zinc oxide) into the rubber composition as one of the essential ingredients of the composition. However, use of a rubber composition containing a zinc-containing compound as a radiator hose, heater hose or radiator packing causes some problems. Thus, zinc eluted into the cooling medium may cause trouble in the mechanical system, and increase electric conductivity to accelerate electrocorrosion of the system. As the result, cracks disadvantageously develop in the radiator hose, heater hose or radiator packing, and to make matters worse, they tend to increase in size.
SUMMARY OF THE INVENTION
In view of the situation, the object of this invention is to provide a rubber composition which comprises as the main component an ethylene-&agr;-olefin copolymer rubber and/or ethylene-&agr;-olefin-non-conjugated diene copolymer rubber, but is free from any zinc-containing compounds that would cause the troubles mentioned above at the time of use of the final products, a vulcanized rubber composition with improved age resistance obtained by vulcanizing the rubber composition, and a radiator hose, heater hose and radiator packing obtained by using the vulcanized rubber composition.
The present inventor has made extensive study to achieve the above-mentioned object and resultantly attained this invention.
Thus, the first aspect of this invention relates to a rubber composition which comprises the following components (A)-(D) and is free from any zinc-containing compounds:
(A): an ethylene-&agr;-olefin copolymer rubber and/or ethylene-&agr;-olefin-non-conjugated diene copolymer rubber,
(B): magnesium oxide,
(C): carbon black,
(D): at least one compound selected from the group consisting of the following compounds (D-1)-(D-3):
(D-1): compounds containing a thio group and a carboxylic acid ester group in the molecule,
(D-2): compounds containing a phenolic hydroxyl group in the molecule,
(D-3): compounds containing an acyl group and an imino group in the molecule.
The second aspect of this invention relates to a vulcanized rubber composition obtained by vulcanizing the above-mentioned rubber composition with an organic peroxide.
The third aspect of this invention relates to a radiator hose, heater hose or radiator packing comprising the above-mentioned vulcanized rubber composition.
DETAILED DESCRIPTION OF THE INVENTION
Component (A) of this invention is an ethylene-&agr;-olefin copolymer rubber and/or ethylene-&agr;-olefin-non-conjugated diene copolymer rubber. The &agr;-olefin in the ethylene-&agr;-olefin copolymer rubber and the ethylene-&agr;-olefin-non-conjugated diene copolymer rubber can be, for example, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and 1-decene, and particularly preferred among them is propylene. The non-conjugated diene can be, for example, chain-like non-conjugated dienes, such as 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene and 7-methyl-1,6-octadiene; cyclic non-conjugated dienes, such as cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, and 6-chloromethyl-5-isopropenyl-2-norbornene; and trienes, such as 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2-norbornadiene, 1,3,7-octatriene and 1,4,9-decatriene. The ethylene-&agr;-olefin-non-conjugated diene copolymer rubber can include one, two or more of these non-conjugated dienes. Particularly preferred among them are 1,4-hexadiene, dicyclopentadiene and 5-ethylidene-2-norbornene. The ethylene-&agr;-olefin copolymer rubber or the ethylene-&agr;-olefin-non-conjugated diene copolymer rubber can be used as oil-extended rubbers containing an extending oil.
The molar ratio of ethylene to &agr;-olefin (ethylene/&agr;-olefin) in component (A) is usually in the range of 40/60-85/15. When a diene is used, the diene content is not more than 20% by weight relative to the total weight of the ethylene, &agr;-olefin and diene.
Component (B) of this invention is magnesium oxide, which is also called magnesia. The magnesium oxide used is not particularly limited and can be those commonly used in the art.
The amount of component (B) used ranges preferably 1-40 parts by weight, more preferably 3-20 parts by weight, relative to 100 parts by weight of component (A). When the amount of component (B) is too small, the age resistance of the vulcanized rubber composition is insufficient in some cases; whereas when it is too large, the age resistance-improving effect hits a ceiling to result in economical disadvantage in some cases. When an oil-extended rubber is used as component (A), the weight of component (A) (100 parts by weight) used as the basis for the other components does not include the weight of the extending oil.
Component (C) of this invention is carbon black and is used for securing high levels of strength and weather resistance of the vulcanized rubber composition. The amount of component (C) used ranges preferably 10-200 parts by weight, more preferably 40 -140 parts by weight, relative to 100 parts by weight of component (A).
Component (D) of this invention is at least one compound selected from the group consisting of the following compounds (D-1)-(D-3):
(D-1): compounds containing a thio group and a carboxylic acid ester group in the molecule,
(D-2): compounds containing a phenolic hydroxyl group in the molecule,
(D-3): compounds containing an acyl group and an imino group in the molecule.
Compound (D-1) can be for example pentaerythritol-tetrakis(&bgr;-lauryl thiopropionate), and “Sumilizer-TP-D” (a trade name, mfd. by Sumitomo Chemical Co., Ltd.) can be used as a corresponding product. Compound (D-2) can be for example 3,9-bis[2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, and “Sumilizer GA80” (a trade name, mfd. by Sumitomo Chemical Co., Ltd.) can be used as a corresponding product. Compound (D-3) can be for example 3-(N-salicyloyl)amino-1,2,4-triazole, and ADEKASTAB CDA-1 (a trade name, mfd. by Asahi Denka Kogyo K.K.) can be used as a corresponding product.
The amount of component (D) used ranges preferably 0.5-20 parts by weight, more preferably 1-10 parts by weight, relative to 100 parts by weight of component (A). When the amount of component (D) is too small, the age resistance of the vulcanized rubber composition is insufficient in some cases; whereas when the amount of component (D) is too large, the age resistance-improving effect hits the ceiling to result in economical disadvantage in some cases. When two or more compounds are used as component (D) in combination, the amount of component (D) herein referred to is the sum of the amount of the two or more c
Sumitomo Chemical Company Limited
Yoon Tae H.
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