EPDM elastomers are produced by three different processes: the solution process, the suspension process (also known as the slurry process), and the gas-phase process. Conventional Ziegler-Natta catalyst systems based on transition metals, such as V and Ti, are commercially used for most of these processes. Currently, metallocene catalyst systems based on Zr, Ti, or Hf also attract the industry's attention for EPDM production. Du Pont/Dow Elastomer, a joint venture between Du Pont and Dow Chemical, has started to produce EPDM by a solution process using Dow’s Insite™ metallocene catalyst. The gas-phase process developed by Union Carbide is also recently commercialized. In this report, we evaluate and compare these processes, which use either ethylidene norbornene (ENB) or 1,4-hexadiene (HD) as the nonconjugated diene in the terpolymer, and either Ziegler-Natta or metallocene catalyst systems for polymerization. The processes can be briefly described thus:

• Solution process for EPDM containing HD by Ziegler-Natta catalyst—the EPDM(HD) elastomer is made in a process presumably used commercially by Du Pont; the polymer is recovered without steam-stripping.

• Solution process for EPDM containing ENB by Insite™ metallocene catalyst—the EPDM(ENB) elastomer is produced in a manner similar to the solution process for EPDM(HD), but this process uses a high polymerization temperature, which allows a high resin concentration in the reactor effluent.

• Solution process for EPDM containing ENB by Ziegler-Natta catalyst—the EPDM(ENB) elastomer is produced in a conventional process with steam-stripping to recover the polymer.

• Gas-phase process for EPDM containing ENB by prepolymerized Ziegler-Natta catalyst—the EPDM(ENB) elastomer is made in a process presumably similar to the commercial process used by Union Carbide.

• Suspension process for EPDM containing ENB by Ziegler-Natta catalyst—the EPDM(ENB) elastomer is produced in excess propylene.