Process Economics Program Report 4B
Ethylene Propylene Terpolymer Rubber
Published: July 1981
Most commercial ethylene-propylene copolymer rubber now includes a small amount of diene to permit conventional vulcanization with sulfur. This EPDM terpolymer is used in non-tire automotive parts, and is used increasingly as an impact modifier for plastics.
Asymmetric nonconjugated dienes are preferred for making EPDM, and three different dienes are used commercially. They are trans-1,4- hexadiene (HD), dicyclopentadiene (DCPD), and 5-ethylidene-norbornene-2 (ENB). These dienes vary in price and also confer different combinations of properties on the final rubber product.
No new EPDM processes have been proposed in recent years, and processes evaluated here are refinements of processes evaluated earlier. Process Improvements have focused on reducing reactor fouling while making more concentrated solutions, increasing catalyst efficiency, and reducing energy requirements for polymer workup.
This report presents technical and economic evaluations of the two processes that are used commercially for making EPDM. Solution processes for making EPDM with HD and for making EPDM with ENB are evaluated. A suspension process for making EPDM with ENB is also evaluated.
The suspension process appears to have capital and operating cost advantages over the solution process, largely because of its lower utllity costs. The solution process that uses hexadiene has a lower cost than the process that uses ENB. This lower cost is attributable to the assumed lower cost for the diene, and to the simplified recovery procedure (which may also be applicable to ENB-containing terpolymers).