process for producing elastomers comprising ethylene, alpha olefins and optionally an diene

摘要

The process for producing an ethylene/a-olefin or ethylene/a-olefin/diene monomer elastomer having a density of 0.850g/cm2 to 0.895 g/cm2 comprises: a) contracting in a first reactor ethylene, at least one aliphatic a-olefin, optionally at least one diene, an activated catalyst comprising a group 4 metal metallocene and a solvent; b) contracting in a second reactor ethylene, at least one aliphatic a-olefin, optionally at least one diene, an activated catalyst comprising a group 4 metal metallocene, a solvent and the high molecular weight fraction of the elastomer from the first reactor; c) removing an elastomeric product stream from the second reactor; d) removing solvent from the elastomeric product stream from the second reactor in an anhydrous first stage solvent recovery operation such that the solid concentration of elastomeric product stream is increased by at least 100% and e) removing additional solvent in an anhydrous second stage solvent recovery operation from the elastomeric product of the first stage solvent recovery operation such that the solid concentration of elastomeric product stream is in excess of 65%. The first reactor is operated such that a high molecular weight fraction of the elastomer is produced at a solid concentration of 1 to 15% weight based on the weight of the reaction mass in the first reactor. The second reactor is operated such that a low molecular weight fraction of the elastomer is produced at a solid concentration of 2 to 30% weight based on the weight of the reaction mass in the second reactor.