Vapor phase polymerization of 1,3‐butadiene with sodium

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Abstract
Apparatus and technique have been described for the polymerization of 1,3‐butadiene in the vapor phase with sodium as catalyst. Research grade butadiene or that obtained from alcohol is necessary for production of high molecular weight polymers by this method. Unmodified polymerizations with increased sodium surface go faster and produce polymers of lower gel content and inherent viscosity. Increase in polymerization temperature reduces the rate, gel content, and inherent viscosity. The chemical structure of the modifier seems to be the predominant factor in its efficiency within a concentration range of 0.1 to 1.0 %. Ethyl chloride is the most powerful modifier of those examined, followed in order by dimethylamine, acetaldehyde, and acetoue. Gelfree polymers with average inherent viscosities of the whole sol between 0.4 and 4.6 were vulcanized and evaluated. The weight distribution was found to be rather narrow for the low viscosity polymers but to become broader as the average inherent viscosity of the polymer increased. Optimum processing and tensile properties were obtained on the polymers of medium viscosity. The dynamic properties of the vulcanizates improve with increase in average inherent viscosity of the raw polymer; the ethyl chloride modified polymer is exceptionally good. The physical properties of the vulcanizate of a blend of equal parts of five polymers of inherent viscosity 1.0 to 4.6 were near those of the lowest molecular weight polymer.