A New Class of Ethylene—Propylene—Diene Terpolymers Produced from Constrained Geometry Metallocene Catalysts

Abstract

Abstract Until recently, ethylene/propylene/diene (EPDM) terpolymers have been manufactured exclusively using vanadium based Ziegler—Natta catalyst systems. The vanadium based catalysts are known to have both product and process limitations. These limitations are due to a complex combination of factors including monomer reactivity, catalyst activity, reactor temperatures and pressures. Single-site metallocene constrained geometry catalyst (CGC) technology enables the manufacture of EPDM terpolymers at higher reactor temperature and catalyst efficiency than standard Ziegler—Natta catalyst systems. The unique combination of monomer, catalyst and process technology enables the manufacture of highly crystalline EPDMs having ethylene contents over 90 wt %. This study investigated these new highly crystalline EPDM terpolymers and their differentiation from commercially available EPDMs. The results indicated that these new EPDMs had very high green strength and barrier properties, yet could be cured by conventional vulcanization techniques. The cure response of these EPDMs to either peroxide or sulfur increased with increasing ethylene content. Sulfur cured vulcanizates had much higher tensile strength than peroxide cured vulcanizates. These new EPDMs demonstrated utility as additives to enhance the abrasion, hot tear, and tensile properties of natural rubber compounds. Sponge compounds, having the unique combination of polyethylene physical properties and the utility of sulfur vulcanization were developed from these new polymers.