Ethylene‐butadiene copolymers, 1. Preparation with modified vanadium catalysts

Abstract

The copolymerization of ethylene with 1,3-butadiene to give crystalline, homopolymer-free, high molecular weight, substantially linear copolymer is described. Butadiene polimerizes almost exclusively in a trans-l,4 structure, ranging in content from zero to 50 mole-%. At relatively low content of butadiene monomeric units ( 5 3 0 mole-%) X-ray crystallinity is of polyethylene type with a slight variation of the structural parameters. At higher levels of butadiene monomeric units, crystallinity of rrans-1,4-polybutadiene is also observed. The products with little unsaturation (1-5 mole-%) melt at about 132°C and are able to crosslink with sulfur-based recipes. A 13C'NMR study shows a block-type structure, but the copolymer appears homogeneous in composition. The product of the reactivity ratios was evaluated. The catalyst system consists of vanadium tris(acetylacetonate), diethylaluminium chloride, and an acidic compound or its precursor. The nature and the amount of the acidic modifier regulate the polymerization rate as well as the molecular weight, composition, and long branching of the copolymer, so that a strict control of the catalyst system is required. The behaviour of the catalyst is tentatively explained by the polarity of the active carbon-vanadium bond, which depends on substituents and complexing agents. Pritchard et

Dienes Polymerization: Where We Are and What Lies Ahead

“…At higher temperatures, homogeneous vanadium catalysts (VOCl 3 or VCl 4 /Al­[N­(CH 3 ) 2 ] 3 /Al­(C 2 H 5 )­Cl 2 ) have been reported to copolymerize dienes and olefins by ENICHEM researchers. The distribution of the butadiene monomeric units, though nonrandom, was sufficiently homogeneous at low monomeric unit content of butadiene (1–3 mol %). − …”

Homo‐ and Copolymerization of Butadiene Catalyzed by an Bis(imino)pyridyl Vanadium Complex

“…[4] Despite the huge number of papers published on this subject, few data are available to date on ethylenebutadiene copolymerization catalyzed by the same compounds. [5] Ethylene-butadiene copolymers are of value for practical applications and cannot be prepared with conventional Ziegler-Natta catalysts or Group 4 metallocenes. Indeed, the presence of butadiene in the feed dramatically depresses the activity of these catalysts in the polymerization of 1-olefins; copolymers with very low incorporation of the conjugated diene monomers are typically obtained.…”

Investigation of Ethylene/Butadiene Copolymers Microstructure by 1H and 13C NMR

“…1 Other vanadium systems are able to copolymerize butadiene and olefins at higher temperatures. 2 The 13 C NMR analysis performed by Bruzzone et al showed that the copolymers synthesized have a block-type structure. Block copolymers have also been obtained with heterogeneous Ziegler-Natta catalysts.…”