Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1996-12-10
1998-03-31
Lipman, Bernard
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
5253317, 5253318, 525348, 525349, 525350, 525387, C08F 800
Patent
active
057339830
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a heat-resistant rubber composition comprising an ethylene-.alpha.-olefin-nonconjugated polyene copolymer rubber. More particularly, the invention relates to a vulcanizable heat-resistant rubber composition having high crosslinking efficiency given by an organic peroxide and capable of providing a vulcanized rubber molded product showing not only excellent mechanical and electrical properties but also prominently high thermal aging resistance, specifically a vulcanizable heat-resistant rubber composition having extremely good fluidity (molding processability).
BACKGROUND ART
Crosslinking of ethylene-.alpha.-olefin copolymer rubbers is carried out using not sulfur, but organic peroxides, because the copolymers have no double bond in their main chains. The rubbers have been used for automotive parts, industrial packing, electrical wires and electrical wire connecting parts, but these parts are desired to be produced at a low cost. For reducing the production cost, it is included to decrease an amount of an organic peroxide crosslinking agent. In these methods, however, the crosslinking is insufficiently performed, resulting in problems of low modulus and poor resistance to permanent set.
On the other hand, since ethylene-.alpha.-olefin-nonconjugated diene copolymer rubbers prepared by copolymerizing ethylene, .alpha.-olefins and nonconjugated polyenes have higher crosslinking efficiency given by an organic peroxides than ethylene-.alpha.-olefin copolymer rubbers, the amount of the organic peroxide can be decreased. However, with respect to the ethylene-.alpha.-olefin-nonconjugated diene copolymer rubber using 1,4-hexadiene, dicyclopentadiene or 5-ethylidene-2-norbornene as the nonconjugated diene, crosslinking is still insufficiently performed, and the thermal aging resistance is low because a large number of double bonds remain after the crosslinking reaction.
By the way, ethylene-propylene copolymer rubbers or ethylene-propylene-diene copolymer rubbers formed by a diene such as ethylidene norbornene, cyclopentadiene or 1,4-hexadiene have excellent mechanical and electrical properties. Moreover, they shows high thermal aging resistance and weathering resistance because they have no double bond in their main chains. Therefore, these rubbers have been widely used for automotive parts, industrial rubber parts, electrical parts and civil engineering and building materials, as described above. In the fields of automotive parts and electrical parts and the like, however, the ethylene-propylene copolymer rubbers and the ethylene-propylene-diene copolymer rubbers have been recently desired to have much higher thermal aging resistance and fluidity (molding processability).
In order to improve a fluidity of the ethylene-propylene copolymer rubbers, a method of adding oils as plasticizers to the copolymer rubbers is generally utilized. In the ethylene-propylene copolymer rubbers prepared utilizing this method, however, there reside problems that the thermal aging resistance of the molded product is lowered and an oil transfer phenomenon (i.e., bleeding) takes place to markedly reduce commercial values.
Further, a method of adding plastics such as polyethylene to the ethylene-propylene copolymer rubbers is also utilized to improve the fluidity. In the ethylene-propylene copolymer rubbers prepared utilizing this method, however, there generally reside problems of low heat resistance and poor elastomeric properties.
Furthermore, an ethylene copolymer rubber composition which is imparted with good processability (fluidity) by blending an ethylene-.alpha.-olefin-polyene copolymer rubber having a different molecular weight is proposed in Japanese Patent Publication No. 14497/1984. However, this rubber composition does not show such high thermal aging resistance as desired.
On the other hand, some examples of conventional methods to improve the thermal aging resistance are described below.
(1) An anti-aging agent is added to the ethylene-propylene copolymer rubber or the e
REFERENCES:
patent: 3407158 (1968-10-01), Gaglielmino et al.
patent: 3817952 (1974-06-01), Knabeschuh et al.
patent: 4268637 (1981-05-01), Weldy
patent: 5278204 (1994-01-01), Tojo et al.
Abstract of Japanese Laid-Open Patent Publ. No. 55-036251 (Mar. 13, 1980).
Abstract of Japanese Laid-Open Patent Publ. No. 60-023433 (Feb. 6, 1985).
Hakuta Takashi
Hosoya Mikio
Kawasaki Masaaki
Tojo Tetsuo
Lipman Bernard
Mitsui Petrochemical Industries Ltd.
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