Ethylene propylene diene terpolymers produced with a homogeneous and highly active zirconium catalyst

Abstract

EPDM terpolymers with ethylidene norbornene as diene monomer could be prepared by means of a soluble Ziegler catalyst formed from biscyclopentadienyl zirconium dimethyl and methylaluminoxane. The overall activities lie between 100 and 1000 kg EPDM/(molZr h bar), obtainable at zirconium concentrations as low as 5 × 10−7 mol/L. After an induction period (0.5–5 h) the polymerization rates increased and then leveled to a value which was constant for several days. From copolymerization kinetics reactivity ratios r12 = 31.5, r21 = 5 × 10−3, and r13 = 3.1 could be derived, and by 13C‐NMR spectroscopy r12 · r21 = 0.3 was found (1: ethylene, 2: propylene and 3: ethylidene norbornene). The regiospecifity of the catalyst toward propylene leads exclusively to the formation of head‐to‐tail enchainments. The diene polymerizes via vinyl polymerization of the cyclic double bond, and the tendency to branching is low. Molecular weights were estimated between 40,000 and 160,000. The average molecular weight distribution of 1.7 is remarkably narrow. Glass transition temperatures of −60 to −50°C could be observed. The cure behavior and the physical properties of cured samples were also tested.

The discovery of metallocene catalysts and their present state of the art

“…Between 1980 and 1987 we synthesized the following copolymers for the first time with metallocene catalysts using the complexes Cp 2 Ti(CH 3 ethylene -propylene (EP) 45 ethylene -propylene, diene (EPDM) 46 ethylene -1-butene (LLDPE) 47 ethylene -1-hexene (LLDPE) 46 ethylene -1,5-hexadiene (elastomer) 46 ethylene -cyclopentene (COC) 48 ethylene -cycloheptene (COC) 48 ethylene -cyclooctene (COC) 48 ethylene -1,3-butadiene (elastomer) 47 ethylene -isoprene (elastomer) 47 While the comonomers are distributed randomly in the polymer chain, only low amounts are needed to decrease the density and the melting point. The low amount of oligomers compared to copolymers produced with Ziegler-Natta catalysts is responsible for a high tensile strength and other mechanical properties of the obtained LLDPE.…”

Ethylene–Propylene–Silsesquioxane Thermoplastic Elastomers

“…More recently, however, there have been many research efforts on the synthesis of EPDMs using metallocene-based catalysts, which give unimodal polymer distributions with sufficiently high molecular weights, good propylene and diene incorporation, relatively low polydispersities, and easier removal of cocatalysts. [27][28][29][30][31][32] In one example, a series of metallocene catalysts were used to synthesize EPDMs, using MAO cocatalysts. [32] One catalyst, ethyl(bis-indenyl)hafnium dichloride, was able to synthesize EPDM elastomers with high molecular weights (M w > 500 000 g Á mol À1 ), relatively low polydispersities (%2-2.5), and good comonomer incorporations.…”

Metallocene Catalysts

“…Metallocene catalysts are suitable for different copolymerizations (Table 4) (85)(86)(87)(88). Copolymers with new microstructures are obtained.…”