There is provided an ethylene--olefin-non-conjugated diene copolymer
rubber satisfying the following requirements (1) to (4):
- (1) a ratio of a Z-average molecular chain length (Az) measured according
to a gel permeation chromatography to a number average molecular chain length (An),
Az/An, of the ethylene--olefin-non-conjugated diene copolymer rubber is
from 20 to 30,
- (2) a ratio of a weight average molecular chain length (Aw), which is
an index of a molecular weight distribution, to the number average molecular chain
length (An), Aw/An, of the ethylene--olefin-non-conjugated diene copolymer
rubber is more than 5,
- (3) a unimodal or bimodal molecular weight distribution structure having
a molecular chain length component, which component is present in a maximum amount
in a range of 3.8Log Aw4.5, exists in the ethylene--olefin-non-conjugated
diene copolymer rubber, and
- (4) a viscosity (ML1+4, 121 C.) of the ethylene--olefin-non-conjugated
diene copolymer rubber measured with a ML viscometer is more than 60 and less than 160.
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