Hydrogenation of Butadiene Rubber

Abstract

Abstract 1. Solutions of butadiene rubber were hydrogenated at atmospheric pressure and room temperature on the following catalysts: palladium on calcium carbonate; palladium on nickel, platinum black from platinum dioxide, platinized carbon activated with doses of chloroplatinous acid, and Raney nickel. 2. It was established that when butadiene rubber is hydrogenated on these catal sts the activity of the catalyst decreases, evidently owing to its surface being obstructed with products of hydrogenation. It was consequently impossible to study the behavior of the double bonds in butadiene rubber on the basis of the curves of the rate of hydrogenation. 3. Specimens of butadiene rubber were prepared at various degrees of hydrogenation on all these catalysts and the following quantities were measured : total unsaturation, proportion of external and internal double bonds, index of refraction, relative viscosity of 0.08 per cent benzene solutions, and vitrification temperature. 4. It was established that when butadiene rubber is hydrogenated on the catalysts studied the external double bonds of the rubber are hydrogenated more rapidly than are the internal bonds. 5. It was established that an increase in the degree of hydrogenation of butadiene rubber leads to a decrease in the index of refraction, relative viscosity of benzene solutions, and vitrification temperature. 6. The decrease in the index of refraction of rubber during hydrogenation shows the absence of cyclization and can be explained by the disappearance of the double bonds of the rubber molecule. 7. It was shown that the decrease in viscosity of benzene solutions of butadiene rubber with increase in the degree of hydrogenation is due to changes in the shape of the rubber molecule during hydrogenation.