Preparation And Properties Of Rare Earth Metal-based Cis-polybutadiene By Gas Polymerization

High cis-1,4-polybutadiene, as the global second general synthetic rubber, is widely used for rubber products and tire manufacturing and a very important national strategic resources. Nowadays, industrial 1,4-polybutadiene is mainly produced by solution polymerization, in which too much solvent is demanded and causes high energy cost, high economic cost and serious environmental pollution. Gas polymerization is a promising technology to overcome the weakness of solution polymerization to produce high cis-1,4-polybutadiene and it is environmental friendly with low energy cost and economic costing. However, the main challenge in gas polymerization of butadiene is the aggregation and adhesion of polymer particles. In order to solve this problem, silica was introduced into polymerization system, as dispersant, which can adhere onto the surface of polymers and reduce the viscosity of surface to prevent polymer aggregation. Meanwhile silica can reinforce the properties of butadiene rubber. Three parts are included in this dissertation as follows:Part one:A supported neodymium-based catalyst was prepared and the gas polymerization of butadiene was investigated. The preferable polymerization temperature is 50℃ and the activity of catalyst can reach to 1006 kg/(molNd·h). The polybutadienes are obtained with the molecular weight of 150,000～400,000 and the molecular weight distribution of 3-8 and its glass transition temperature is-107℃.Part two:The influences of dispersant species, amount and feeding strategy on the morphology of 1,4-polybutadiene were systematically studied. The experimental results showed that SiO2 dispersant with large size is much better for the diffusion of catalyst. As the increase of dispersant amount, polymerization activity also increased. The morphology of polymers could be adjusted from aggregation state to particle state by changing the feeding strategy of dispersant. The polybutadiene particles produced by gas polymerization could be stored for 30 days at room temperature without obvious cold flow and aggregation, and the angle of repose remained below 60°. The problem of polybutadiene aggregation and adhesion was successfully solved during gas polymerization.Part three:The processing properties and tensile properties of polybutadienes obtained under different polymerization conditions were investigated. The tensile properties of polybutadiene can be improved and the Mooney viscosity could be reduced by proper feeding strategy of dispersant. In comparison with the traditional solution polymerization, polybutadienes bygas phase polymerization usually have higher molecular weight, higher Mooney viscosity and better tensile properties.