| abstract |
The rubber composition of the invention is a vulcanizable blend obtained by microdispersing, in a molten state, a polyolefin resin (B) in an ethylene/Α-olefin/nonconjugated polyene copolymer rubber (A) made from ethylene, an Α-olefin of 3 to 20 carbon atoms and a nonconjugated polyene. The average dispersed particle diameter of the polyolefin resin (B) is not more than 2 mu m, and the blending ratio of the component (B) to the component (A), [(B)/(A)], is 5/95 to 50/50. Polyolefin resin (B) difficult to microdisperse in a rubber kneader can easily do so when it is kneaded with additives such as reinforcing agent, filler, softener, vulcanization facilitator and vulcanizing agent. By using the composition, the polyolefin resin (B) can be reliably and sufficiently dispersed in a short time by a conventional kneading machine of the rubber industry; a rubber product of high stability and quality can be readily supplied at low costs. The process for preparing rubber composition according to the invention comprises the steps of feeding a rubber mixture (E) containing 100 parts by weight of an ethylene/Α-olefin/nonconjugated polyene copolymer rubber (A) and 3 to 10 parts by weight of an organic solvent (D) to a multi-stage vented extruder through its feeding zone, feeding a polyolefin resin (B) to the extruder through another feeding zone in an inert gas atmosphere, and kneading the rubber mixture (E) and removing the solvent to obtain well-microdispersed, blocking-free vulcanizable ethylene copolymer rubber composition pellets containing the ethylene/Α-olefin/nonconjugated polyene copolymer rubber (A) and the polyolefin resin (B). |